♪ NARRATOR: IN NOVEMBER, 2018, A 34-YEAR-OLD CHINESE RESEARCHER NAMED HE JIANKUI MADE A STARTLING ANNOUNCEMENT TO THE WORLD VIA YOUTUBE.

TWO BEAUTIFUL LITTLE CHINESE GIRLS NAMED LULU AND NANA CAME CRYING INTO THE WORLD AS HEALTHY AS ANY OTHER BABIES.

NARRATOR: WORKING IN SECRET, HE HAD TAKEN THE POWER OF HEREDITY INTO HIS OWN HANDS.

FOR THE FIRST TIME, HE HAD INTENTIONALLY ALTERED A GENE IN THE EMBRYOS OF TWIN GIRLS-- AN ALTERATION THAT WOULD BE PASSED ON TO THEIR CHILDREN AND THEIR CHILDREN'S CHILDREN, DOWN THROUGH THE GENERATIONS.

CHANGING THE GENETIC CODE OF THE HUMAN RACE... FOR GENERATIONS.

FOR GENERATIONS.

[APPLAUSE] NARRATOR: THE ANNOUNCEMENT TRIGGERED IMMEDIATE CONDEMNATION.

MAN: I PERSONALLY DON'T THINK THAT IT WAS MEDICALLY NECESSARY.

WHY IS THERE SO MUCH SECRECY?

NARRATOR: HE'S WORK, CRITICS SAID, WAS "ARROGANT," "PREMATURE," "IRRESPONSIBLE", EVEN "MONSTROUS."

THIS IS A RED LINE.

WHY DID YOU CHOOSE TO CROSS THIS LINE?

NARRATOR: CROSSING A SCIENTIFIC RUBICON BEFORE THE ETHICS OR THE TECHNOLOGY HAD BEEN FULLY CONSIDERED.

IN THE UNITED STATES, THIS KIND OF ACTION WOULD HAVE BEEN FRANKLY ILLEGAL.

I FEEL DEEPLY DISTURBED.

IT'S INAPPROPRIATE AND SOMETHING THAT WE HAD BEEN WORKING HARD TO AVOID.

NARRATOR: BUT BEHIND THE OUTCRY WAS A RECOGNITION: THIS MOMENT HERALDED THE ARRIVAL OF A NEW ERA, AN ERA IN WHICH HUMANS ARE NO LONGER AT THE MERCY OF THEIR GENES, BUT CAN CONTROL AND EVEN CHANGE THEM.

IT IS A SCIENTIFIC REVOLUTION OF ALMOST UNLIMITED PROMISE AND PERIL.

MAN: GENES CONTAIN A HISTORY OF OURSELVES, OUR ANCESTRY, AND BY DEFINITION, THEY CONTAIN OUR FUTURE, BECAUSE WE WILL PASS THEM ALONG FOR GENERATIONS.

THE CHALLENGE WITH ALL THESE TECHNOLOGIES IS THAT DNA IS NOT JUST A GENETIC CODE.

IT IS IN SOME SENSE ALSO A MORAL CODE.

IT DOESN'T JUST ASK QUESTIONS ABOUT WHAT WE WILL BECOME.

NOW THAT WE HAVE THESE TOOLS, WE HAVE THE CAPACITY TO ASK THE QUESTION: WHAT CAN WE BECOME?

NOW THAT I CAN CHANGE DNA AND THEREBY CHANGE OUR FUTURE, WHAT WILL I DO?

♪ NARRATOR: DR. WENDY CHUNG IS A GENE HUNTER.

FROM HER LAB AT COLUMBIA UNIVERSITY MEDICAL CENTER, ON HEART DISEASE, CANCER, AND AUTISM.

BUT HER PASSION IS THE UNIVERSE OF MORE THAN 5,000 RARE DISEASES.

♪ ♪ CHUNG IS TRYING TO HARNESS A REVOLUTION IN GENETICS TO FIND, AND PERHAPS BLOCK, THE GENES THAT CAUSE RARE DISEASE.

SO, WE'LL GO AHEAD AND GET STARTED.

WE'RE GOING TO HAVE A FEW CASES THAT WE'RE TALKING ABOUT THIS MORNING... CHUNG, VOICE-OVER: WHEN I GREW UP, IN MEDICAL SCHOOL, AS A RESIDENT, WE KNEW ABOUT THESE CONDITIONS, AND WE JUST HAD NOTHING TO OFFER, AND IT'S VERY, VERY DIFFERENT NOW.

THIS IS A BRAND-NEW ERA IN TERMS OF GENOMIC MEDICINE.

HEY, HOW ARE YOU?

GOOD TO SEE YOU.

OK, COME ON AROUND.

LET'S HAVE A SEAT.

NARRATOR: CHUNG WORKS CLOSELY WITH FAMILIES OF CHILDREN SHE TREATS TO RAISE AWARENESS OF RARE DISEASES.

CHUNG: THANKS, EVERYONE, FOR COMING OUT TONIGHT.

UM, WE'RE GOING TO USE THE TIME TO GIVE SOME UPDATES, AND SO, I THOUGHT WE'D JUST START WITH UPDATES IN TERMS OF HOW EVERYONE'S DOING... NARRATOR: BECAUSE THEIR CHILDREN'S DISEASES ARE SO UNCOMMON, THEY HAVE BEEN LARGELY IGNORED BY DRUG COMPANIES AND THE GOVERNMENT.

THEY MUST RELY ON EACH OTHER AND ON A FEW INTERESTED SCIENTISTS LIKE DR. CHUNG.

CHUNG: ONE OF THE THINGS THAT I THINK YOU'RE AWARE OF BUT JUST TO BE--PUT OUT THERE IS THAT, AT LEAST FOR 3 OF YOU, YOU HAVE UNDERTAKEN THE HERCULEAN TASK OF PUTTING ON FAMILY MEETINGS THIS SUMMER.

LUKE, DO YOU WANT TO SHARE?

LUKE: SURE.

SO, WE'RE HAVING A CONFERENCE IN AUGUST.

I HOPE YOU ALL CAN COME BECAUSE THAT'S REALLY IMPORTANT TO ME, TOO, IS HAVING... NARRATOR: LUKE ROSEN AND SALLY JACKSON HAVE A 4-YEAR-OLD DAUGHTER, SUSANNAH, WHO HAS A RARE DEGENERATIVE CONDITION THAT AFFECTS HER MOTOR SKILLS AND COGNITION.

JACKSON: IT WAS A NORMAL PREGNANCY AND, YOU KNOW, NORMAL DELIVERY.

SHE WAS BORN AT 39 WEEKS.

AND THE PEDIATRICIAN CAME IN AND SAID, "SHE'S PERFECT!"

[SUSANNAH FUSSING] SHE CAME HOME AND SHE WAS CRANKY.

SHE WAS CRANKY.

SHE CRIED A LOT.

SHE MADE HER MILESTONES, BUT JUST BARELY.

TOY: THAT WAS FUN.

LET'S PLAY AGAIN!

JACKSON, VOICE-OVER: AND THEN WHEN SHE WAS CRAWLING, SHE... SHE WAS JUST PULLING HER LEGS BEHIND HER, SO, IT WASN'T EVEN A REAL CRAWL.

AND THEN ONE DAY, I HAD HER IN THE BATHTUB, AND SHE WAS SITTING IN HER BATH CHAIR, AND I SAID, "COME ON, SHA-SHA, KICK, KICK, KICK!"

AND SHE DIDN'T.

LATER, WHEN I WOULD SAY AGAIN IN THE BATH, "KICK, KICK, KICK," SHE WOULD REACH DOWN AND LIFT UP ONE OF HER LEGS.

NARRATOR: AS THEIR CONCERNS GREW, THE ROSENS SOUGHT HELP.

SUSANNAH UNDERWENT TEST AFTER TEST BUT NO ONE COULD FIGURE OUT WHAT WAS WRONG.

JACKSON: OK, FINE, JUST THIS ONE MRI, THIS ONE HALF-HOUR EEG.

THEY'RE NOT GOING TO FIND ANYTHING.

PLEASE.

AND I WANT TO DO IT, OF COURSE, BECAUSE I WANT TO GET THE ALL-CLEAR.

UM...YEAH.

I FEEL LIKE I'M STILL GETTING OVER THAT THERE WASN'T AN ALL-CLEAR.

NARRATOR: FINALLY, A TEST REVEALED THAT SUSANNAH HAD AN ANOMALY IN A GENE KNOWN TO BE INVOLVED IN MUSCLE CONTROL.

HER FATHER LUKE SOUGHT THE ADVICE OF A NEUROLOGIST.

ROSEN: I SAT DOWN AT HER DESK, AND SHE SAID, "TELL ME WHAT IT IS AGAIN."

AND I SAID, "K-I-F-1-A...GENE."

I COULD TELL SHE HAD TO TELL ME SOMETHING THAT WAS HORRIBLE.

SHE PRINTED SOMETHING OUT AND HANDED ME THIS PIECE OF LITERATURE.

THEN SHE SAID, "WE DON'T KNOW ENOUGH ABOUT IT.

WE DON'T KNOW WHAT IT IS."

JACKSON: I THINK SHE SAID THOSE HORRIBLE WORDS WHICH WERE, "TO ENJOY EVERY DAY THAT YOU HAVE WITH HER."

THAT IS A CONDOLENCE CARD.

I DON'T WANT A SYMPATHY NOTE, I WANT--I WANT SOME ANSWERS.

I WANT SOME INFORMATION.

AND THEN SOMEONE SAID, "YOU REALLY SHOULD SEE WENDY CHUNG."

CHUNG: I ACTUALLY REMEMBER VERY DISTINCTLY THE DAY.

I WAS DOWN AT A GENETICS MEETING IN ALABAMA AND I GOT THIS URGENT CALL, AND LITERALLY AS SOON AS WE GOT A COFFEE BREAK, I GOT ON THE PHONE WITH LUKE AND SALLY AND I COULD TELL THEY WERE IN A STATE OF CONFUSION AND PANIC, BECAUSE THEY WEREN'T SURE EXACTLY WHAT THIS MEANT.

KIF1A IS A GENE, WHAT WE CALL A MOLECULAR MOTOR.

TO BE ABLE TO MOVE YOUR BODY THE WAY YOU WANT TO, YOU HAVE TO GET SIGNALS FROM YOUR BRAIN TO YOUR MUSCLES.

IT'S LIKE A RAILROAD, AND KIF1A IS THE LOCOMOTIVE THAT'S MOVING THINGS ALONG THE RAILROAD.

NARRATOR: THESE SIGNALS ARE TRANSPORTED ALONG NERVE CELLS, AND PROTEINS MADE BY THE KIF1A GENE KEEP THOSE NERVE CELLS HEALTHY.

BUT WHEN THE GENE IS CORRUPTED, THE SIGNALS CAN'T GET THROUGH AND THE NERVE CELLS DIE.

THAT IS WHAT IS HAPPENING TO SUSANNAH.

ROSEN: WENDY SAID, "SUSANNAH IS LIKELY "GOING TO BE IN A WHEELCHAIR.

"SHE IS GOING TO HAVE VISION PROBLEMS, "AND SHE'S CERTAINLY, UM, GOING TO HAVE A VERY CHALLENGING AND PROBABLY NOT FULL LIFE."

BOY: SUSIE'S DOING SOME MORE OF THE KNEE BENDING.

CHUNG: SOME INDIVIDUALS MAY INITIALLY START OUT BY WALKING OR TALKING.

BUT WITH TIME, INSTEAD OF CONTINUING AS NORMAL CHILDREN DO, WHAT'S MOST TRAGIC ABOUT THIS CONDITION IS THAT THOSE CHILDREN THEN PLATEAU AND THEN ACTUALLY START TO DECLINE.

AND THAT, AS FAR AS WE CAN TELL SO FAR, IS A ONE-WAY STREET.

NARRATOR: IS SUSANNAH'S FATE ALREADY INSCRIBED IN HER GENES, OR CAN HER PARENTS AND DOCTOR FIND A WAY TO SLOW, OR EVEN HALT, THE PROGRESSION OF HER ILLNESS?

JACKSON: WENDY SAID TO US, "WHAT WE WANT TO DO IS MAKE SUSANNAH'S BRAIN A SUPERHIGHWAY."

SO, RIGHT NOW, WE'RE JUST FOCUSING ALL THIS ENERGY ON MAKING SURE THAT, YOU KNOW, IT'S NOT A ONE-LANE ROAD, IT'S NOT A TWO-LANE HIGHWAY, IT HAS ALL THE LANES.

JUST KEEP ON BUILDING THEM OUT.

MAKE EVERYTHING AS STRONG AND AS GOOD AND SUPPORTED AND ADVANCED AS IT CAN BE BECAUSE THE ROAD IS GOING TO START TO CRUMBLE.

AND THOSE LANES ARE GOING TO DROP OFF.

AND WHEN THEY DO, THE MORE YOU HAVE TO BEGIN WITH AND THE STRONGER THEY ARE, THE MORE YOU'LL HAVE LEFT.

SUSANNAH: RAWR!

JACKSON: FANCY PANTS.

NARRATOR: HOW DO WE BECOME WHO WE ARE?

WHY ARE WE LIKE OUR PARENTS, AND WHY ARE WE DIFFERENT?

FOR CENTURIES, THE WORLD'S GREATEST THINKERS HAVE PONDERED THE MYSTERY OF HUMAN HEREDITY.

MAN: THIS IS THE STORY OF ONE OF HUMANKIND'S MOST EXTRAORDINARY JOURNEYS.

I MIGHT EVEN SAY IT IS THE MOST EXTRAORDINARY JOURNEY.

IT IS A JOURNEY TO FIND WHAT IT IS THAT MAKES OURSELVES.

THE QUESTION THAT LINGERS IS THE CENTRAL QUESTION: WHY ARE HUMAN BEINGS LIKE EACH OTHER AND WHY ARE WE UNLIKE EACH OTHER?

IS IT BECAUSE GOD WILLED IT TO BE THIS WAY OR IS THERE A PROCESS?

NARRATOR: IN ANCIENT GREECE, PYTHAGORAS BELIEVED THAT SPERM ABSORB MYSTICAL VAPORS FROM THE BODY AND PASS THEM ON.

ARISTOTLE THOUGHT BOTH PARENTS CONTRIBUTE TRAITS, NOT THROUGH VAPORS OR ANY KIND OF PHYSICAL MATTER, BUT BY THE PASSING ALONG OF SOME KIND OF MESSAGE-- INFORMATION--THAT DETERMINES THE NEXT GENERATION.

IN TIME, THESE THEORIES AND OTHERS WOULD YIELD TO THE BELIEF IN AN ALL-POWERFUL GOD WHO GOVERNS ALL CREATION.

IN THIS VIEW, EVERYTHING WE ARE AND WILL BE IS PREDETERMINED, REGARDLESS OF OUR PARENTAGE.

MAN: FOR A LONG TIME IN THE HISTORY OF BIOLOGY, THERE WAS A VERY PERSUASIVE IDEA CALLED PREFORMATIONISM.

AND THE IDEA IS THIS: THAT IN EACH SPERM OR IN EACH EGG, DEPENDING ON WHAT YOUR PREFERENCE IS, IS A TINY, COMPLETE PERSON.

EVERY PERSON FROM THE TIME OF ADAM AND EVE CONTAINS WITHIN HIM OR HER AN EXACT, FULLY FORMED, BUT TEENY HUMAN, AND SO, ONE IS INSIDE THE OTHER, IS INSIDE THE OTHER, IS INSIDE THE OTHER FOR ETERNITY.

BERRY: THESE ARE RUSSIAN DOLLS.

THAT'S A SORT OF PLEASING IDEA IF YOU BELONG TO AN ERA WHICH BELIEVES IN AN OMNIPOTENT, ALL-POWERFUL CREATOR WHO CREATED EVERYTHING.

THIS SOLVES THE PROBLEM.

EVERYTHING WAS CREATED ON DAY ONE AND ALL WE'RE DOING IS, IF YOU LIKE, GRADUALLY ROLLING OUT THAT CREATION.

NARRATOR: BY THE BEGINNING OF THE 19th CENTURY, IT WAS CLEAR THAT THE THEORY OF PREFORMATIONISM HAD ONE OBVIOUS FLAW: IF ALL LIFE IS PREDETERMINED BY GOD, HOW IS IT POSSIBLE FOR HUMANS TO INTERVENE?

FARMERS HAD ALREADY FIGURED OUT HOW TO BREED FLOWERS THAT BLOOMED LONGER, CATTLE THAT PRODUCED MORE MILK, AND SHEEP WITH THICKER WOOL.

A NEW THEORY FOR HEREDITY WAS NEEDED TO EXPLAIN, AND ULTIMATELY IMPROVE UPON, THESE HUMAN INTERVENTIONS.

MAN: IN THE 1800S, PEOPLE BEGAN TO GET REALLY INTERESTED IN WHAT YOU COULD DO WITH BREEDING PLANTS AND ANIMALS.

THERE WAS INTEREST IN ENGLAND, SPAIN, ALL OVER THE CONTINENT.

BUT THE PLACE THAT WAS MOST INTERESTED IN THIS WAS THE AUSTRO-HUNGARIAN EMPIRE, IN THE CITY OF BRNO.

NARRATOR: ON THE OUTSKIRTS OF BRNO STOOD AN AUGUSTINIAN MONASTERY CALLED ST. THOMAS.

ITS ABBOT WAS CYRIL NAPP, A PRACTICAL MAN AS INTERESTED IN THE MECHANISMS OF NATURE AS THE MYSTERIES OF THE ALMIGHTY.

MAN: THE MONASTERY OWNED LOTS OF ORCHARDS AND PRODUCED LOTS OF GRAIN.

AND ABBOT NAPP WAS INTERESTED IN HOW THEY COULD INCREASE PRODUCTION.

HE SAID, "LOOK, RATHER THAN WORRYING ABOUT ALL THESE BREEDING SCHEMES, WE SHOULD REALLY BE ASKING THE KEY QUESTION, WHICH IS "WHAT IS INHERITED AND HOW?"

NARRATOR: NAPP WENT LOOKING FOR MONKS WHO SHARED HIS FASCINATION WITH FACTS, AS WELL AS FAITH.

ONE OF THEM WAS A YOUNG MAN NAMED GREGOR MENDEL, A POOR FARMER'S SON WHO HAD FLOUNDERED AT NEARLY EVERYTHING HE TRIED BEFORE ENTERING THE MONASTERY IN 1853.

HE'D BEEN TOO TONGUE-TIED FOR THE PULPIT AND TWICE FAILED TESTS TO BECOME A SCHOOL TEACHER, BUT HE HAD STUDIED MATH AND PHYSICS, WHICH GAVE HIM A FRESH PERSPECTIVE ON HEREDITY.

THE ABBOT PUT HIM TO WORK EXPLORING THE LAWS OF INHERITANCE.

HIS "LABORATORY" WAS A NEWLY CONSTRUCTED GREENHOUSE, WHICH STOOD BESIDE A SMALL GARDEN PLOT.

HERE, WORKING WITH HIS OWN CROP OF PEA PLANTS, MENDEL CARRIED OUT ONE OF THE MOST IMPORTANT EXPERIMENTS IN SCIENTIFIC HISTORY.

MUKHERJEE: MENDEL BEGAN BY IDENTIFYING 7 CHARACTERISTICS IN PEA PLANTS.

IT COULD BE THE COLOR OF A FLOWER.

IT COULD BE THE TEXTURE OF THE ACTUAL PEA.

THEN HE CROSSBRED THEM.

LANDER: WHAT HE FOUND WAS WHEN HE TOOK A STRAIN THAT HAD ROUND SEEDS AND A STRAIN THAT HAD WRINKLED SEEDS AND HE CROSSED THEM TOGETHER, THE OFFSPRING HAD ROUND SEEDS.

SO, HE CALLED ROUND THE "DOMINANT TRAIT" BECAUSE WHEN YOU CROSS THESE TWO STRAINS TOGETHER, IT DOMINATED.

WRINKLED WAS THE "RECESSIVE TRAIT."

WHEN YOU LOOKED AT THE PROGENY, THOSE PROGENY WERE COMPLETELY ROUND.

WRINKLED WAS GONE.

IT HAD COMPLETELY RECEDED AWAY.

NARRATOR: BUT MENDEL DID NOT STOP THERE.

HE NEXT CROSSED THE HYBRIDS WITH EACH OTHER AND MADE A REMARKABLE DISCOVERY.

THE TRAITS THAT HAD DISAPPEARED IN THE SECOND GENERATION REGULARLY REAPPEARED IN SUBSEQUENT ONES.

MUKHERJEE: THAT WAS A SURPRISE.

HOW COULD YOU TAKE A PIECE OF INFORMATION, MAKE IT VANISH FOR ONE GENERATION, AND THEN HAVE IT REAPPEAR?

AND THE ONLY WAY THAT WOULD BE TRUE IS IF THE INFORMATION IS ELEMENTAL, DOES NOT GET ERASED.

IT CAN BE SUPPRESSED, IT CAN BE HIDDEN, BUT IT REMAINS INTACT ACROSS GENERATIONS.

NARRATOR: FASCINATED BY WHAT HE WAS FINDING, MENDEL CONTINUED THE EXPERIMENT, BREEDING AND CROSSBREEDING HIS EVER-EXPANDING FAMILY OF PEA PLANTS, AND METICULOUSLY RECORDING EVERY STEP OF THE PROCESS.

HENIG: OVER THE COURSE OF THE 7 YEARS THAT HE WAS STUDYING PEAS, THERE WERE THOUSANDS AND THOUSANDS OF PLANTS.

40,000 BLOSSOMS AND 300,000 PEAS THAT HE HAD TO PULL OUT AND LOOK AT AND CHARACTERIZE AND WRITE DOWN.

NARRATOR: NO MATTER HOW MANY GENERATIONS MENDEL CROSSED, A SIMPLE PATTERN HELD: DOMINANT TRAITS APPEARED FAR MORE OFTEN, BUT THEY DID NOT ERASE OR BLEND WITH RECESSIVE TRAITS.

SUCH A PATTERN COULD MEAN ONLY ONE THING, MENDEL CONCLUDED.

WHATEVER MYSTERIOUS "FACTORS" UNDERLIE DOMINANT AND RECESSIVE TRAITS, THEY REMAIN WHOLE AND INTACT GENERATION AFTER GENERATION.

WOMAN: I THINK WHAT WAS REALLY REVOLUTIONARY ABOUT MENDEL'S FINDINGS WAS THAT HE, WITHOUT EVER USING THE WORD "GENE," HE LAYS OUT, IN SUCH A COMPELLING AND CONVINCING WAY, THE WAYS IN WHICH TRAITS GET PASSED FROM ONE GENERATION TO THE NEXT, AND HE CHANGED THE WAY WE THINK ABOUT THE WORLD.

NARRATOR: MENDEL PUBLISHED HIS SEMINAL RESULTS IN AN OBSCURE JOURNAL IN 1866.

BY THEN, CHARLES DARWIN'S THEORY OF EVOLUTION HAD REVOLUTIONIZED SCIENTIFIC THINKING.

BUT NO ONE SAW THE CONNECTION.

MUKHERJEE: WHAT FOLLOWS WAS ONE OF THE STRANGEST SILENCES IN THE HISTORY OF SCIENCE.

THIS IS THE FOUNDING PAPER OF MODERN BIOLOGY.

BUT ALL OF THESE FINDINGS WHICH ARE METICULOUSLY DOCUMENTED BASICALLY VANISH.

NARRATOR: THEN, IN 1900, 3 BOTANISTS WORKING INDEPENDENTLY REDISCOVERED MENDEL'S PAPER AND REPEATED HIS EXPERIMENTS.

SUDDENLY, THE OBSCURE MONK WAS NEARLY AS FAMOUS AS DARWIN HIMSELF.

BUT THERE WERE STILL MANY QUESTIONS SURROUNDING THE THEORY.

IF MENDEL WAS RIGHT, AND TRAITS WERE THE EXPRESSION OF INFORMATION PASSED DOWN IN DISCRETE UNITS, WHERE WAS THAT INFORMATION STORED?

A GERMAN SCIENTIST NAMED THEODOR BOVERI PROVIDED AN ANSWER.

STUDYING THE FILAMENT-LIKE STRUCTURES IN CELLS CALLED "CHROMOSOMES," BOVERI IDENTIFIED THEM AS THE LOCATION OF MENDEL'S ELUSIVE FACTORS.

BOVERI HAD SUPPLIED THE SITE.

A DANISH RESEARCHER-- WILHELM JOHANNSEN-- GAVE THEM A NAME: "GENES."

THE WORD "GENE" IS BORN AS AN ABSTRACTION.

NO ONE KNOWS WHAT IT IS, NO ONE KNOWS HOW TO DESCRIBE IT.

IS IT A CHEMICAL?

IS IT A VAPOR?

IS IT A SUBSTANCE?

DOES IT HAVE ATOMS?

DOES IT HAVE MOLECULES IN IT?

WE DON'T KNOW.

AT THE TURN OF THE CENTURY, PEOPLE ARE STILL STRUGGLING TO DESCRIBE WHAT IT IS.

NARRATOR: LITTLE PROGRESS WAS MADE UNTIL THE 1910S, WHEN AN OBSESSIVE COLUMBIA UNIVERSITY BIOLOGIST NAMED THOMAS HUNT MORGAN BEGAN A SERIES OF EXPERIMENTS WITH FRUIT FLIES.

LANDER: THOMAS HUNT MORGAN WAS A PRETTY UNLIKELY CHOICE TO BE ONE OF THE WORLD'S BEST GENETICISTS BECAUSE IN THE EARLY PART OF THE 20th CENTURY, HE WAS ENORMOUSLY SKEPTICAL ABOUT GENETICS.

HE WAS SCATHING ABOUT GENETICS.

NARRATOR: TO MORGAN, IT WASN'T CLEAR THAT GENES EXISTED AT ALL, LET ALONE THAT ANYTHING SO TINY COULD POSSIBLY PRODUCE THE DAZZLING COMPLEXITY OF LIFE.

FROM WITHIN HIS LAB, NICKNAMED "THE FLY ROOM," MORGAN SET OUT TO DISPROVE MENDEL'S THEORIES.

LANDER: COMPARED TO A GARDEN IN THE MIDDLE OF A MONASTERY IN MORAVIA, THE FLY ROOM COULD NOT HAVE BEEN MORE DIFFERENT.

IT WAS A CRAMPED ROOM WITH LITTLE GLASS VIALS AND COTTON STOPPERS AND LOTS OF FRUIT FLIES.

IT WAS A RADICALLY DIFFERENT ENVIRONMENT, BUT IT WAS THE PERFECT PLACE.

BECAUSE YOU CAN ONLY GET A FEW GENERATIONS OF PEAS GOING EACH YEAR.

FRUIT FLIES, EVERY TWO WEEKS YOU GET A NEW GENERATION.

AND YOU COULD TRY ALL SORTS OF EXPERIMENTS.

NARRATOR: MORGAN OBSESSIVELY CATALOGUED THE FRUIT FLY TRAITS.

HE WAS NOT LOOKING FOR SIMILARITIES, HE WAS LOOKING FOR DIFFERENCES.

ONLY IN VARIATION COULD PATTERNS OF HEREDITY BE REVEALED.

MUKHERJEE: MORGAN UNDERSTANDS THAT ONCE IN A WHILE, THERE'LL BE A CHARACTERISTIC IN A FLY THAT IS DIFFERENT FROM ALL THE OTHER FLIES.

IT'S AN OUTLIER.

AND BY TRACKING THAT CHARACTERISTIC, HE CAN ILLUMINATE SOMETHING ABOUT THE NATURE OF WHY FLIES ARE THE WAY THEY ARE.

IT'S AN ASTONISHING IDEA: AN OUTLIER HELPS US UNDERSTAND NORMALCY.

AND THAT OUTSIDE CHARACTERISTIC BECOMES LIKE A BEACON.

IT BECOMES LIKE A BEACON OF LIGHT THAT HE CAN FOLLOW IN THE DARKNESS.

NARRATOR: MORGAN AND HIS STUDENTS TRIED TO FORCE CHANGES, OR "MUTATIONS," IN THEIR FRUIT FLIES, SUBJECTING GENERATION AFTER GENERATION TO A BATTERY OF ABUSES, FROM DIZZYING RIDES IN CENTRIFUGES, TO BLISTERING HEAT, TO SHATTERING COLD.

FOR MORE THAN TWO YEARS, THEY WATCHED AND WAITED, HOPING TO TRIGGER THE APPEARANCE OF A SINGLE OUT-OF-THE-ORDINARY TRAIT.

COBB: NOTHING HAPPENED.

HE WAS ABOUT TO GIVE UP WHEN HE DISCOVERED IN ONE OF HIS STOCKS, THESE BOTTLES OF FLIES, A WHITE-EYED INDIVIDUAL.

THIS WHITE-EYED INDIVIDUAL HE COULD THEN BREED FROM, JUST AS MENDEL HAD DONE, AND WAS ABLE TO SHOW THAT THIS WAS IN FACT A GENE, THIS HAD A GENETIC BASIS.

NARRATOR: AS HE FOLLOWED THE DESCENDANTS OF THE WHITE-EYED FLY, MORGAN DISCOVERED THAT THE TRAIT WAS CARRIED ACROSS GENERATIONS INTACT, JUST AS THE WRINKLED TRAIT HAD BEEN IN MENDEL'S PEAS.

LANDER: HE'S SEEING THESE "PREDICTABILITIES," EVERYTHING FOLLOWING THESE LAWS.

HE BECOMES, WITHIN A FEW YEARS, A TOTAL CONVERT TO MENDELISM.

IT'S A FANTASTIC TRANSFORMATION.

AND THEN, UNDERSTANDING AND BELIEVING THESE LAWS, HE TAKES IT FAR BEYOND WHERE MENDEL HAD EVER GONE.

NARRATOR: AS HE DELVED DEEPER, MORGAN MADE A DISCOVERY THAT SEEMED TO CONTRADICT MENDEL'S FINDINGS.

RATHER THAN EACH TRAIT BEING INHERITED INDEPENDENTLY OF EVERY OTHER TRAIT, MORGAN NOTICED THAT SOME FRUIT FLY TRAITS SEEMED TO BE INHERITED TOGETHER, AS IF PHYSICALLY LINKED.

FLIES WITH RED EYES HAD LARGE ANTENNAE; FLIES WITH BROWN EYES, CURLED WINGS.

MUKHERJEE: HE BEGINS TO UNDERSTAND THAT THESE UNITS OF INFORMATION ARE NOT, LIKE MANY PEOPLE HAD SUPPOSED THEM TO BE, INDEPENDENTLY SCATTERED IN SPACE.

WHEN ONE MOVES FROM THE PARENT TO THE OFFSPRING, IT BRINGS ANOTHER PIECE ALONG WITH IT.

MORGAN BEGINS TO NOW RE-VISUALIZE GENES NOT AS ABSTRACT ENTITIES.

HE BEGINS TO SAY, "WELL, "THEY SORT OF LOOK LIKE THINGS THAT ARE STRUNG ALONG, LIKE BEADS ON A STRING."

NARRATOR: THE "BEADS" MORGAN DESCRIBED WERE GENES; THE STRINGS, CHROMOSOMES.

SOMETIMES, THE BEADS ARE REARRANGED DURING REPRODUCTION.

WHEN THIS HAPPENS, THE GENES CLOSEST TOGETHER ARE MORE LIKELY TO REMAIN TOGETHER, WHICH ACCOUNTS FOR THE LINKAGE OF TRAITS.

THOSE FURTHER APART ARE MORE LIKELY TO BECOME SEPARATED, OR "DE-LINKED."

WORKING BACKWARDS BY OBSERVING PATTERNS OF LINKAGE, MORGAN BEGAN TO GATHER DATA ABOUT THE PHYSICAL DISTANCE BETWEEN ANY TWO UNDERLYING GENES.

BUT WHAT COULD THIS TELL HIM?

LANDER: AS USUAL, IT TOOK A REALLY SMART KID TO FIGURE IT OUT.

IT WAS A SOPHOMORE IN 1911-- ALFRED STURTEVANT.

NARRATOR: THE SON OF A MATHEMATICIAN-TURNED-FARMER, STURTEVANT HAD BEEN OBSESSED WITH INHERITANCE SINCE HIS BOYHOOD IN ALABAMA, WHEN HE MAPPED OUT HIS FAMILY'S GENEALOGY AND TRACED THE PEDIGREES OF HIS FATHER'S HORSES.

LANDER: EVERYBODY ELSE WAS WORKING ON THEIR OWN EXPERIMENTS GENERATING LOTS OF DATA ABOUT TRAIT NUMBER ONE AND TRAIT NUMBER TWO AND HOW THEY WERE CORRELATED AND TRAIT NUMBER 4 AND TRAIT NUMBER 5.

STURTEVANT JUST TOOK HOME EVERYBODY'S DATA ABOUT THE CORRELATIONS AND INHERITANCE BETWEEN GENES AND HE PULLED THE GREATEST ALL-NIGHTER IN THE HISTORY OF SCIENCE.

NARRATOR: BY ANALYZING ALL OF THE DATA TOGETHER, STURTEVANT WAS ABLE TO CREATE A FULL PICTURE THAT SHOWED WHERE MANY FLY GENES WERE LOCATED RELATIVE TO EACH OTHER ON FLY CHROMOSOMES.

LANDER: AND WHAT STURTEVANT DID IN THAT EPIC ALL-NIGHTER WAS HE INVENTED THE CONCEPT OF GENETIC MAPPING.

IF I HAVE A GENE HERE AND A GENE HERE ON THE SAME CHROMOSOME AND I HAVE ANOTHER GENE THAT'S CORRELATED IN ITS INHERITANCE WITH THIS ONE AND WITH THIS ONE, WE CAN TELL WHERE IT LIVES.

NARRATOR: MORGAN AND HIS STUDENTS HAD PROVED THAT GENES MUST BE PHYSICAL OBJECTS ARRANGED IN A PREDICTABLE ORDER ALONG A CHROMOSOME.

BUT THEY COULD NOT ANSWER TWO BIGGER QUESTIONS: DO GENES REALLY CONTAIN THE INSTRUCTIONS THAT MAKE UP LIFE, AND, IF SO, WHAT IF THOSE INSTRUCTIONS CONTAIN A MISTAKE?

[PEOPLE TALKING AT ONCE] HI.

I'M DR. WENDY.

HOW ARE YOU?

VERY NICE TO MEET YOU.

NARRATOR: OVER THE LAST 20 YEARS, DR. WENDY CHUNG HAS IDENTIFIED OVER 40 PREVIOUSLY UNKNOWN GENETIC CAUSES OF RARE DISEASES.

CHUNG: MUY BIEN.

OTRA VEZ.

[INHALES] MUY BIEN, MUY BIEN.

NARRATOR: IT IS DAUNTING DETECTIVE WORK.

SHE RELIES ON HER CLOSE RELATIONS WITH PATIENTS AND THEIR FAMILIES TO HELP HER TRACK DOWN CLUES.

CHUNG, VOICE-OVER: THEY LOOK TO ME FOR HONESTY.

THEY LOOK TO ME IN TERMS OF BEING ABLE TO GIVE IT TO THEM STRAIGHT, BUT KNOWS WHAT THEY FEEL LIKE WHEN THEY'RE LYING AWAKE IN THE MIDDLE OF THE NIGHT, THAT HAS THE SAME PASSION, THE SAME DRIVE, THE SAME ENERGY, THAT IS WITH THEM AT MIDNIGHT WHEN WE'RE BOTH UP WORRYING ABOUT THESE THINGS, WHO IS LITERALLY WITH THEM EVERY STEP OF THE WAY AND NOT ABOUT TO STOP.

BABY DOLL LAY DOWN THERE.

IS YOUR BABY DOLL HERE?

NARRATOR: DR. CHUNG'S RESEARCH WAS NOT ALWAYS SO INTIMATELY INVOLVED WITH CHILDREN AND FAMILIES.

SHE STARTED HER CAREER AS A BASIC SCIENTIST, WORKING MOSTLY IN THE LAB.

CAN YOU SQUEEZE MY FINGER?

NARRATOR: BUT THEN, SOMETHING HAPPENED THAT CHANGED EVERYTHING.

OH, LOOK HOW STRONG YOU ARE.

CHUNG, VOICE-OVER: I LIKE TO THINK THAT I LIVED A CHARMED LIFE FOR MANY YEARS.

HAVE A WONDERFUL HUSBAND.

I HAD A WONDERFUL SON.

HAD A WONDERFUL CAREER.

GOT TO DO SCIENCE AND THINK ABOUT VERY INTERESTING PUZZLES.

AND THEN I JUST LEARNED THAT LIFE IS NOT PREDICTABLE AND WE WERE NOT AS CHARMED AS I WISH WE COULD HAVE BEEN.

CHECKUP FOR BABY?

YOU WANT TO DO A CHECKUP FOR THE BABY?

LET'S PUT ON YOUR WHITE COAT THEN.

NARRATOR: DR. CHUNG AND HER HUSBAND LOST THEIR SECOND SON.

AFTER A PROFOUND PERIOD OF SOUL-SEARCHING, SHE DECIDED TO REFOCUS HER CAREER.

CHUNG, VOICE-OVER: I KNEW THAT MY JOB WAS NOT TO BECOME THE WORLD'S GREATEST EXPERT IN ONE LITTLE THING.

WHAT I NEEDED TO DO WAS SOMETHING THAT MADE A DIFFERENCE IN THE LIVES OF MY PATIENTS, AND FROM THAT DAY FORWARD, THAT BECAME MY MISSION.

SO, ESPECIALLY THE KIDS-- KIDS LIKE SUSANNAH.

I GET TO HAVE...BE A MOM TO MANY, MANY, MANY WONDERFUL KIDS AND THEY'VE BECOME MY EXTENDED FAMILY, AND THAT'S WHAT FILLS THE HOLE.

THAT'S WHAT FILLS THE VOID.

SHE'S SLEEPING A LITTLE BIT MORE... OK, WE'LL LET HER SLEEP A LITTLE BIT MORE.

CHUNG: IT'S LATE.

IT'S THE END OF A LONG DAY.

ARE YOU TIRED?

ROSEN, VOICE-OVER: WHAT'S INCREDIBLE ABOUT DR. CHUNG IS THE WAY SHE GETS DOWN ON THE SAME LEVEL AS SUSANNAH AND LOOKS AT HER AND JUST PLAYS WITH HER.

HAVING THAT PLAYTIME IS A CLINICAL EVALUATION BECAUSE THERE AREN'T ANY TOOLS TO CAPTURE WHAT'S GOING ON WITH SUSANNAH.

BUT I THINK IT'S MORE ABOUT, JUST A REALLY INCREDIBLE RESEARCHER AND DOCTOR WHO HAS THIS CONNECTION WITH OUR DAUGHTER.

CHUNG: OOH.

LOOK AT THAT.

NARRATOR: TOGETHER, DR. CHUNG AND THE ROSENS HAVE SET OUT TO FIGHT THE PROGRESSION OF SUSANNAH'S DISEASE.

[LAUGHTER] CHUNG, VOICE-OVER: THIS IS NOT SOMETHING THAT IS GOING TO, WITH A LOT OF HARD WORK, GO AWAY IN A FEW MONTHS.

IT'S A LONG JOURNEY.

IT'S LIKE CLIMBING MOUNT EVEREST.

IT REALLY IS THAT BIG A MOUNTAIN THAT WE'VE GOT TO BE ABLE TO CLIMB.

JACKSON: YOU KNOW, WENDY SAID THIS WONDERFUL THING.

"I CAN BE INVOLVED AS MUCH OR AS LITTLE AS YOU WANT "IN THIS PROCESS, AND IF YOU WANT ME TO I WILL BE YOUR SHERPA."

AND YOU'RE LIKE, "YES, I WANT YOU TO BE MY SHERPA!

"IF YOU ARE LEADING THE EXPEDITION, THANK YOU.

COUNT ME IN."

ROSEN: WE HAVE 5 YEARS, I THINK.

5 YEARS BEFORE THINGS GET TOO TRICKY TO CORRECT.

SO, WE WANT TO ACCOMPLISH THIS MISSION THAT WE HAVE BEFORE SHE'S IN A WHEELCHAIR, NOT SPEAKING, AND HAVING TOO MANY SEIZURES.

NARRATOR: WHEN CHUNG AND THE ROSENS BEGAN TO LOOK FOR A TREATMENT FOR SUSANNAH, THEY BARELY KNEW WHERE TO START.

THE KIF1A MUTATION WAS SO RARE THAT NO ONE HAD STUDIED IT IN ANY DETAIL.

ROSEN: THE BASIC FUNCTION OF THE GENE WAS NOT REALLY KNOWN.

AND WE DIDN'T KNOW WHAT THE FUNCTION OF THE GENE IS BECAUSE WE DIDN'T HAVE A CLINICAL PICTURE OF PEOPLE WHO HAVE IT BECAUSE THERE WEREN'T MANY PEOPLE WHO WERE IDENTIFIED TO HAVE IT.

SO, ONE OF THE FIRST THINGS THAT WENDY SAID IS WE GOT TO FIND 100 KIDS.

AND THAT BECAME THE ACTIONABLE STEP.

VERY LOGICAL.

LET'S GO FIND 100... HOW DO WE, HOW DO WE .... DO THAT?

NARRATOR: LUKE LAUNCHED A WEBSITE AND BEGAN TO SPREAD THE WORD ABOUT KIF1A.

CHUNG: THERE ARE SOME PEOPLE WHO JUST HAVE A VISION, AND THEY KNOW HOW TO COMMUNICATE, AND I THINK LUKE KNEW HOW TO DO THAT VERY EFFECTIVELY, MUCH MORE EFFECTIVELY THAN I DID.

AND SO, HE STARTED RELENTLESSLY BRINGING THE COMMUNITY TOGETHER.

HELLO.

HELLO.

HI.

HOW ARE YOU?

HI, GUYS.

ROSEN: WE'RE PROBABLY NOT GOING TO BE ABLE TO GET TO ALL... ROSEN, VOICE-OVER: 20, 30, 40, 50, 60, 70, AND, YOU KNOW, LESS THAN A YEAR LATER, WE WERE AT 75 OR 80 KIDS.

NARRATOR: AS THE COMMUNITY OF KIF1A PATIENTS GREW, SO DID THE HOPE THAT THEY WOULD ATTRACT THE ATTENTION OF DRUG COMPANIES.

BUT CHUNG AND OTHER RESEARCHERS KNEW THAT THEY WOULDN'T BE ABLE TO INJECT EXPERIMENTAL DRUGS DIRECTLY INTO CHILDREN.

THEY NEEDED SOMETHING THEY COULD EXPERIMENT ON, A PROXY FOR THE CHILDREN, WHICH CONTAINED A MUTATION IN THE KIF1A GENE.

THEY NEEDED A MOUSE.

CHUNG, VOICE-OVER: AT ONE POINT, YOU KNOW, ONE OF THE THINGS I SAID TO LUKE WAS THAT WE NEED A MOUSE.

AND SO, HE GOT THE FAMILIES TOGETHER ON A CAMPAIGN.

HE HAD EACH OF THE FAMILIES TAKE OUT THEIR PHONE AND HAVE THEIR KIDS SING OR CHANT, "WE NEED A MOUSE!"

BOTH: WE NEED A MOUSE!

WE NEED A MOUSE!

WOMAN: WHAT DO YOU HAVE IN YOUR HAND?

A MOUSE!

BOTH: WE NEED A MOUSE!

WE NEED A MOUSE!

NEED MOUSE!

WE NEED A MOUSE!

NEED A MOUSE THAT WEARS A BLOUSE IN YOUR HOUSE.

ROSEN: WE STARTED SENDING THAT AROUND THE WORLD TO EVERYBODY AND PEOPLE REALIZED THAT "I DON'T KNOW WHAT KIF1A IS, BUT THEY NEED A MOUSE."

ALL: WE NEED A MOUSE!

WE NEED A MOUSE!

WE NEED A MOUSE!

MY LITTLE BROTHER NEEDS A MOUSE.

WE NEED A MOUSE!

WE NEED A MOUSE!

WE NEED A MOUSE.

DON'T WE?

YEAH.

[VOCALIZING] YEAH.

CHUNG, VOICE-OVER: LUKE WOVE TOGETHER THIS ENTIRE STORYBOOK OF FAMILIES, EACH IN THEIR OWN WAY, BEING ABLE TO SHOW THEMSELVES AND SHOW HOW UNITED THEY WERE.

WE NEED A MOUSE!

WE NEED A MOUSE.

WE NEED A MOUSE!

WE NEED A MOUSE!

WE NEED MOUSE.

WE NEED A MOUSE!

BOTH: ♪ WE NEED A MOUSE ♪ BOTH: WE NEED A MOUSE!

ROSEN: SUSANNAH, WHAT DO YOU SAY?

THANK YOU!

YEAH!

CHUNG, VOICE-OVER: AND, SO, NOW WE HAVE A MOUSE.

NARRATOR: IN THE SECOND HALF OF THE 19th CENTURY, GREGOR MENDEL HAD WORKED OUT THE BASIC LAWS OF HEREDITY WITH PEA PLANTS.

AT THE SAME TIME, CHARLES DARWIN HAD OBSERVED THE LARGER PROCESS OF EVOLUTION IN BIRDS AND TORTOISES.

BUT WHAT ABOUT PEOPLE?

WHAT THESE INSIGHTS MEANT FOR THE HUMAN RACE WAS THE NEXT FRONTIER.

AT THE TURN OF THE CENTURY, IN LONDON, A COUSIN OF DARWIN'S NAMED FRANCIS GALTON, A BRILLIANT SCIENTIST IN HIS OWN RIGHT, ASKED HIMSELF A PROVOCATIVE QUESTION: IF FARMERS COULD BREED BETTER CATTLE, WHY COULDN'T AN ENLIGHTENED SOCIETY BREED A BETTER HUMAN BEING?

"WHAT NATURE DOES BLINDLY" AND "SLOWLY," HE WROTE, "MAN MAY DO PROVIDENTLY" AND "QUICKLY."

MAN: THIS WAS AN AGE OF SCIENCE, AN AGE OF REASON.

DARWIN WAS USING SCIENTIFIC PRINCIPLES TO LOOK AT THE WORLD AND FIGURE OUT THE WORLD.

AND GALTON WAS TAKING THESE SAME SCIENTIFIC IDEAS AND SAYING, "HOW CAN WE ACTUALLY WORK WITH THE HUMAN RACE AND PERFECT IT?"

NARRATOR: GALTON BECAME THE FATHER OF A NEW PSEUDO-SCIENCE THAT WOULD SHADOW GENETICS ACROSS THE 20th CENTURY.

IT WAS CALLED "EUGENICS."

BERRY: EUGENICS BASICALLY MEANS GOOD GENESIS, GOOD INHERITANCE.

AND THAT'S WHAT GALTON IS INTERESTED IN.

SCIENCE CAN SOLVE PROBLEMS AND MAKE THE PLANET A BETTER PLACE.

AND EUGENICS WAS PART OF THAT.

NO LONGER ARE WE SORT OF BEING BUFFETED THROUGH HISTORY BY THE FORCES OF EVOLUTION.

WE'RE GOING TO TAKE CONTROL.

COHEN: DARWIN WAS TALKING ABOUT ADAPTATION TO AN ENVIRONMENT.

THERE WERE CERTAIN SPECIES, CERTAIN PEOPLE WITHIN A SPECIES THAT ADAPTED WELL OR DIDN'T ADAPT.

BUT IT COMES TO US THROUGH EUGENICS AS "HERE ARE THE FIT PEOPLE, AND THEY'RE THE ONES WE WANT, "AND HERE ARE THE INFERIORS, THE UNFIT, AND WE NEED TO GET RID OF THEM."

IT WAS A PERVERSION, BUT IT FIT INTO THEIR VIEW OF THE WORLD.

NARRATOR: GALTON'S VISION OF THE STEADY IMPROVEMENT OF THE HUMAN RACE ATTRACTED MANY LEADING THINKERS IN ENGLAND, FROM WINSTON CHURCHILL TO H.G.

WELLS, BUT NEVER MANAGED TO SPARK A NATIONAL MOVEMENT.

BERRY: WHICH NATION ON THE PLANET REALLY TOOK EUGENICS TO HEART?

IT WASN'T THE EUROPEANS.

IT WAS THE CAN-DO, SOLVE THE PROBLEM AMERICANS.

♪ NARRATOR: IN THE EARLY YEARS OF THE TWENTIETH CENTURY, MIDDLE-CLASS AMERICANS FELT THREATENED BY A VAST UNCONTROLLED INFLUX OF IMMIGRANTS FROM EASTERN AND SOUTHERN EUROPE.

COHEN: THIS IDEA OF EUGENICS HITS AMERICA AT A TIME OF GREAT ANXIETY, A TIME WHEN AMERICAN SOCIETY IS IN FLUX AND PARTICULARLY FOR THE OLD ANGLO-SAXON MIDDLE CLASS, THEY LOOK AROUND AND THE NATION THAT THEY WERE BORN INTO IS GONE.

NARRATOR: GALTON HAD CALLED FOR THOSE WITH TALENT TO IMPROVE THEMSELVES BY SELECTIVE BREEDING.

AMERICAN EUGENICISTS TOOK HIS IDEA A STEP FURTHER.

THOSE DEEMED "INFERIOR"-- THE "FEEBLE-MINDED," "PROMISCUOUS," OR DISABLED-- SHOULD BE STOPPED FROM HAVING CHILDREN ALTOGETHER.

MUKHERJEE: THERE'S A REAL WORRY THAT IT'S NOT ENOUGH TO BREED THE BEST, BUT, TO KEEP THE NATIONAL AVERAGE UP, YOU NEED TO ELIMINATE THE WORST, TO CUT OFF FROM THE BOTTOM THE DISEASED ROOTS OF THE GENETIC TREE.

NARRATOR: WHILE CONGRESS IMPOSED QUOTAS TO BAR "UNDESIRABLE" IMMIGRANTS, 32 STATES PASSED COMPULSORY STERILIZATION LAWS FOR THOSE DEEMED "UNFIT."

SOME 64,000 AMERICANS, MOST OF THEM WOMEN, WERE LEGALLY STERILIZED, NEARLY ALL AGAINST THEIR WILL OR WITHOUT THEIR KNOWLEDGE.

ENTHUSIASM FOR EUGENICS REMAINED HIGH AMONG AMERICANS UNTIL THEY SAW ANOTHER COUNTRY TAKE IT TO ITS LOGICAL-- AND HORRIFYING--CONCLUSION.

ADOLF HITLER, LEADER OF THE RISING NAZI PARTY, FIRST READ ABOUT AMERICAN EUGENICS POLICIES WHILE IN PRISON IN 1924, AND THEY SOON BECAME PILLARS OF NAZI IDEOLOGY.

WOMAN: IN "MEIN KAMPF," HITLER PAID HOMAGE TO AMERICAN EUGENICISTS AND DISPLAYED DEEP KNOWLEDGE OF THEIR WORKS.

IDEAS OF STERILIZATION, IN PARTICULAR, WERE OF INTEREST TO HITLER.

THIS IS A VERY DEEP INTERCONNECTION BETWEEN THE U.S. AND GERMANY AT THIS TIME.

THEY'RE BUILDING ON EACH OTHER'S IDEAS, THEY'RE BUILDING ON EACH OTHER'S LEGISLATION, THEY'RE FUNDING EACH OTHER'S EFFORTS.

MAN: THEY WERE ADOPTING THE STANDARD PRINCIPLES OF EUGENICS, PER THEIR AMERICAN AND BRITISH COLLEAGUES, BY ELIMINATING INFERIOR GENES, WHICH FOR THE NAZIS WERE THE GENES CARRIED BY JEWISH PEOPLE, THE GENES CARRIED BY GYPSIES, THE GENES CARRIED BY HOMOSEXUALS, AND THE OTHER GROUPS THAT THEY FOUND UNDESIRABLE, AND BY SIMPLY REMOVING THESE INDIVIDUALS FROM THE POPULATION, THEY WERE IMPROVING THE GENETIC COMPOSITION OF THE GERMAN PEOPLE.

NARRATOR: EUGENICS WOULD PROVIDE HITLER WITH A JUSTIFICATION FOR HIS CAMPAIGN TO DOMINATE ALL OF EUROPE WITH A GERMAN MASTER RACE.

MUKHERJEE: THIS IDEA THAT YOU CAN REENGINEER HEREDITY, THAT YOU CAN REENGINEER INHERITANCE, THAT WHICH IS MOST CENTRAL TO US.

NOT JUST CULTURE; YOU DON'T JUST BURN BOOKS.

YOU BURN THE CAPACITY OF HUMAN BEINGS TO TRANSMIT THEIR INFORMATION TO THEIR CHILDREN.

YOU CENSOR THE IDEA THAT HUMAN BEINGS ARE FREE TO PASS ALONG TO THEIR CHILDREN THEIR FUNDAMENTAL CHARACTERISTICS.

NARRATOR: LESS THAN 5 MONTHS AFTER ASSUMING POWER IN 1933, THE NAZIS ORDERED THAT ANYONE SUFFERING A HEREDITARY DISEASE MAY BE STERILIZED.

SOON, NEARLY 5,000 STERILIZATIONS WERE BEING PERFORMED IN GERMANY EACH MONTH.

SHEFFER: DRIVING HITLER WAS THIS IDEA OF A RACIALLY PURE VOLK AND, IN ORDER TO REALIZE THIS EUGENICIST VISION, YOU NEED TO ASSEMBLE AS MUCH INFORMATION ABOUT THE CITIZENS AS POSSIBLE, WHICH MEANT COMBING THROUGH SCHOOL RECORDS, MEDICAL RECORDS, DOWN TO EVEN SPORTS CLUB RECORDS, SO THAT EACH INDIVIDUAL WOULD HAVE THEIR OWN FILE.

AND THESE FILES THEN WOULD BECOME THE BASIS FOR DETERMINING AN INDIVIDUAL'S FATE.

NARRATOR: BY THE OUTBREAK OF WORLD WAR II IN SEPTEMBER 1939, THE NAZIS HAD TURNED FROM FORCED STERILIZATION TO MURDER, EUTHANIZING CHILDREN AND ADOLESCENTS CONSIDERED GENETICALLY "DEFECTIVE."

SOON, THEY WERE ELIMINATING ADULTS, TOO, UNDER A PROGRAM CALLED AKTION T4.

THE T4 PROGRAM WAS BOTH A PILOT EXPERIMENT FOR WHAT BECAME THE HOLOCAUST, AND WAS DRIVEN BY MEDICAL BELIEFS ABOUT GENETICS.

FOR PSYCHIATRIC PATIENTS, YOU DIDN'T LEARN THESE BEHAVIORS; YOU WERE BORN WITH INTELLECTUAL IMPAIRMENT, WITH AN INSATIABLE DESIRE TO DRINK, OR PROMISCUITY.

SIMILARLY, IN THE T4 PROGRAM, YOU HAD SOME PEOPLE SAYING, "LOOK, WE ARE KEEPING PEOPLE ALIVE "IN TIMES OF TIGHT RESOURCES, "AND THEY DON'T DESERVE TO BE ALIVE BECAUSE "THEY'RE NOT CONTRIBUTING ANYTHING TO SOCIETY.

WE'VE GOT TO ELIMINATE THEM OR STOP THEM FROM BREEDING."

NARRATOR: IT WAS A SHORT STEP FROM THE GAS CHAMBERS USED IN THE AKTION T4 PROGRAM TO THE GAS CHAMBERS USED IN THE DEATH CAMPS OF TREBLINKA, SOBIBOR, AND AUSCHWITZ.

SHEFFER: THE THIRD REICH WAS REALLY THE ULTIMATE REALIZATION OF POPULATION REENGINEERING.

HITLER WAS OUT TO REMAP EUROPE, TO MOVE POPULATIONS INTO THE COUNTRIES AND STATES WHERE THEY BELONG, TO ERADICATE THE POPULATIONS THAT WERE UNWORTHY OF LIFE, AND TO, YOU KNOW, REALIZE GALTON'S IDEA OF UP-BREEDING THE POPULATION, JUST IN THE MOST MURDEROUS WAY IMAGINABLE.

LANDER: SCIENCE LETS ITSELF BE USED IF YOU DON'T STAND UP EVERY TIME AND SAY, "NO.

THAT'S NOT OK. THAT CONCLUSION IS NOT OK." AND EUGENICS, FROM THE BEGINNING OF THE 20th CENTURY TO THE NAZIS, IS A PERFECT EXAMPLE OF WHAT WE HAVE TO WATCH OUT FOR EVERY TIME WE GO OFF WITH A LITTLE BIT OF SCIENTIFIC KNOWLEDGE AND PRESCRIBE WHAT WE THINK IS RIGHT FOR THE WORLD.

NARRATOR: UNDERLYING EUGENICS HAD BEEN THE IDEA OF GENETIC DETERMINISM-- THAT OUR GENES ARE OUR FATE.

BUT WAS THIS TRUE?

HOW FAR DID THE DOMINION OF THE GENE EXTEND?

THE ANSWERS REQUIRED FIGURING OUT NOT JUST WHAT A GENE IS, BUT HOW IT WORKS.

SCIENTISTS THE WORLD OVER WERE DRAWN TO THIS ENIGMA.

ONE WAS ERWIN SCHRODINGER, A REFUGEE FROM NAZI GERMANY, WHO WOUND UP IN DUBLIN.

A PHYSICIST BY TRAINING, SCHRODINGER APPROACHED THE QUESTION OF THE GENE'S ESSENTIAL MAKEUP WITH THE FRESH PERSPECTIVE OF A BIOLOGY OUTSIDER.

SCHRODINGER: IS IT A CORPUSCLE?

IS IT AN ATOM?

MOLECULE?

NARRATOR: HE DREW ON A NEW SCIENCE EMERGING FROM THE WAR-- INFORMATION TECHNOLOGY-- THE STUDY OF SYSTEMS FOR STORING, RETRIEVING, AND SENDING INFORMATION.

EARLY COMPUTERS, USED TO TARGET ANTI-AIRCRAFT FIRE DURING THE WAR... NEWSCASTER: ALL YOUR CAREFUL PREPARATIONS BEFORE FIRING HAVE BUT ONE PURPOSE: ACCURACY!

NARRATOR: HAD ALREADY SHOWN THAT VASTLY COMPLEX TASKS COULD BE MANAGED BY SIMPLE, REPRODUCIBLE CODES.

LANDER: IT WAS REALLY THE DAWN OF THE INFORMATION AGE IN COMPUTERS AND ALMOST AT EXACTLY THE SAME MOMENT, THE DAWN OF THE REALIZATION THAT BIOLOGY WAS, AT ITS CORE, ABOUT INFORMATION.

NARRATOR: IN 1944, SCHRODINGER PUBLISHED A SLIM VOLUME-- "WHAT IS LIFE?"

IN IT, HE THEORIZES THAT THE INSTRUCTIONS FOR LIFE MUST BE ENCODED ON GENES, LIKE A COMPUTER PUNCH CARD.

COBB: HE SAYS WHAT A GENE IS.

HE SAYS IT'S A PHYSICAL OBJECT, IT'S A MOLECULE, AND IT CONTAINS WHAT HE CALLED A CODE-SCRIPT.

THIS IS THE FIRST TIME THAT ANYBODY HAD THOUGHT ABOUT GENES CONTAINING A CODE.

NARRATOR: IF A GENE IS ESSENTIALLY A CODE, SCHRODINGER REASONED, IT MUST BE SIMPLE AND STABLE ENOUGH TO BE ACCURATELY REPRODUCED ACROSS THOUSANDS OF GENERATIONS-- AND, AT THE SAME TIME, COMPLEX ENOUGH TO CONTAIN SEPARATE INSTRUCTIONS FOR ALL THE WORLD'S RICHLY VARIED LIFE FORMS.

SIMPLE, YET COMPLEX.

DURABLE, YET FLEXIBLE.

A PHYSICAL MOLECULE, BUT WHICH ONE?

[BIRD CHIRPS] HE'S SAYING, "OK, THERE'S THIS SUBSTANCE.

"IT'S COPIED.

IT CAN CHANGE AND MUTATE.

NOW TELL ME WHAT THE CHEMICAL IS."

NARRATOR: ANALYSIS OF CHROMOSOMES HAD SHOWN THAT IT WAS LIKELY TO BE EITHER PROTEINS OR DEOXYRIBONUCLEIC ACID--DNA.

MOST SCIENTISTS, INCLUDING SCHRODINGER, BET ON PROTEINS.

COBB: PROTEINS MAKE UP VIRTUALLY EVERYTHING IN YOUR BODY.

THEY MAKE UP YOUR HAIR, YOUR TEETH, YOUR SKIN, ALL YOUR ORGANS.

THE WAY YOUR BODY FUNCTIONS INVOLVES PROTEINS.

AND PROTEINS ARE MOLECULES THAT ARE VIRTUALLY INFINITE IN THEIR VARIETIES.

NARRATOR: UNLIKE PROTEINS, DNA IS SO SIMPLE THAT SOME SCIENTISTS REFERRED TO IT AS THE "STUPID MOLECULE."

DNA IS MADE UP OF JUST 4 CHEMICAL COMPONENTS, OR BASES, KNOWN BY THE LETTERS "A", "T", "C," AND "G." THE SIMPLICITY OF THE DNA MOLECULE WAS THE REASON WHY SO FEW SCIENTISTS BELIEVED THAT IT WAS ULTIMATELY GOING TO BE THE SOURCE OF HEREDITARY INFORMATION.

IT JUST DIDN'T SEEM POSSIBLE THAT YOU COULD CREATE SOMETHING AS COMPLICATED AS A HUMAN BEING WITH JUST 4 BASIC SUBUNITS.

NARRATOR: MEANWHILE, A LITTLE-KNOWN SCIENTIST NAMED OSWALD AVERY AT THE ROCKEFELLER INSTITUTE IN NEW YORK HAD MADE A SURPRISING DISCOVERY WHILE WORKING WITH BACTERIA.

MUKHERJEE: AVERY PERFORMED AN EXPERIMENT IN WHICH HE ASKED THE QUESTION: OF ALL THE SCHMUTZ OF CHEMICALS THAT COMES OUT WHEN YOU BREAK OPEN SOME BACTERIAL CELL, WHICH CHEMICAL IN THAT BIG CHEMICAL SOUP CARRIES GENETIC INFORMATION?

NARRATOR: TO FIND OUT, AVERY REMOVED ONE CHEMICAL AT A TIME FROM THE BACTERIA, BUT THEY KEPT ON TRANSMITTING THEIR GENETIC INFORMATION UNTIL THERE WAS ONLY ONE CHEMICAL LEFT.

THE ONLY WAY HE CAN STOP THE MOVEMENT OF GENETIC INFORMATION IS IF HE DISTILLS AWAY OR KILLS OR CHANGES DNA, THAT...THAT STUPID MOLECULE.

AND SO, IN A FELL SWOOP, HE SUDDENLY LASER FOCUSES ON DNA AS THE CARRIER OF GENETIC INFORMATION.

DNA IS WHAT IS CARRYING GENES.

NARRATOR: MANY SCIENTISTS REMAINED SKEPTICAL OF DNA, EVEN AFTER AVERY'S EXPERIMENTS.

BUT A BRILLIANT YOUNG AMERICAN SCIENTIST NAMED JAMES WATSON DID NOT.

WATSON: I NEVER DOUBTED DNA WAS IMPORTANT.

BUT IN THE ABSENCE OF HAVING A MOLECULE WHICH YOU COULD SEE IT, IT WAS ALL, YOU SAY, INTELLIGENT BULL ... , AND, YOU KNOW, IT JUST SOUNDED GOOD, BUT NO ONE WAS CONVINCED.

BUT I JUST KNEW DNA WAS THE KEY IF YOU WERE GOING TO UNDERSTAND LIFE.

NARRATOR: WATSON GREW UP ON CHICAGO'S SOUTH SIDE AND ENROLLED AT THE UNIVERSITY OF CHICAGO AT THE AGE OF 15, INITIALLY INTENDING TO STUDY BIRDS.

BUT THE PUZZLE OF DNA DREW HIM.

MUKHERJEE: WHAT ABOUT ITS MOLECULAR STRUCTURE COULD POSSIBLY EXPLAIN IT AS THE CARRIER OF INFORMATION?

HOW COULD YOU GENERATE STRUCTURALLY PROFOUND INTELLIGENCE OUT OF SUCH SEEMING PROFOUND STUPIDITY?

IF YOU WANTED TO UNDERSTAND GENES, WE HAD TO UNDERSTAND DNA.

NARRATOR: AFTER BRIEF STINTS AT A SERIES OF EUROPEAN UNIVERSITIES, WATSON FOUND HIMSELF AT THE CAVENDISH LAB AT CAMBRIDGE UNIVERSITY, WHERE HE GOT TO KNOW FRANCIS CRICK, A FORMER PHYSICIST 12 YEARS HIS SENIOR.

WATSON MEETING CRICK IS ONE OF THE MOST IMPORTANT MOMENTS IN THE HISTORY OF SCIENCE, FULL STOP.

THEY BRING COMPLEMENTARY SKILLS.

NARRATOR: WHERE WATSON WAS INTUITIVE, CRICK WAS LOGICAL.

WHERE WATSON LEAPT, CRICK VENTURED CAUTIOUSLY, STEP BY STEP.

MUKHERJEE: WATSON BRINGS TO THE EQUATION HIS LOVE OF BIOLOGY.

HE COULD NAVIGATE HIS WAY THROUGH SOME OF THE MOST COMPLEX BIOLOGICAL QUESTIONS AND GET TO THE HEART OF IT.

CRICK BRINGS TO IT A KIND OF RIGOR FROM PHYSICS AND CHEMISTRY.

THE GUY WHO SITS NEXT TO YOU ON A TRAIN AND SOLVES YOUR CROSSWORD PUZZLE.

CRICK WAS THAT GUY, IRRITATING, BUT OFTEN RIGHT.

LANDER: THEY KNEW THAT, IF THEY COULD WORK OUT THE STRUCTURE, IT MUST HAVE THE SECRET OF HOW WE WRITE INFORMATION AND TRANSMIT INFORMATION, BUT THEY COULDN'T SAY EXACTLY WHAT THAT WAS AND HOW IT COULD WORK.

AND SO, THEY STARTED BY JUST PULLING THE THREAD AND SAYING, "WHAT'S THE STRUCTURE LOOK LIKE?"

NARRATOR: IN MAY 1951, WATSON AND CRICK BEGAN TRYING TO SOLVE THE PUZZLE OF HOW DNA IS PUT TOGETHER.

THEY ROAMED THE HALLS OF THE CAVENDISH, DEBATING LOUDLY.

MUKHERJEE: THEY WERE ALMOST BANISHED TO A ROOM BECAUSE THEY WERE SO FRUSTRATING TO ALL THE OTHER PEOPLE.

THEY SAID GO AND, LIKE CHILDREN, LIKE THEY WOULD GO TO THE OTHER ROOM AND PLAY.

AND THAT'S WHAT THEY DID--THEY PLAYED.

NARRATOR: FOR MONTHS, THE TWO SCIENTISTS SKETCHED AND BUILT MODELS, REARRANGING THE 4 BASES OF DNA ALONG A MOLECULAR SPINE, FIRST ONE WAY AND THEN ANOTHER.

THEY WERE MODELING.

THEY WERE THINKING.

THEY WERE PLAYING AROUND WITH HOW THINGS COULD FIT TOGETHER, AND COMING UP WITH WACKY SOLUTIONS.

BUT THEY KNEW THEY HAD TO PLAY AROUND WITH THE STRUCTURE TILL THEY GOT IT.

NARRATOR: WHILE WATSON AND CRICK TINKERED, IN LONDON, JUST 50 MILES TO THE SOUTH, AN INTENSE 30-YEAR-OLD RESEARCHER NAMED ROSALIND FRANKLIN WAS DETERMINED TO FIGURE OUT THE STRUCTURE OF DNA A DIFFERENT WAY: BY TAKING A PICTURE OF IT.

FRANKLIN HAD EARNED A PLACE IN THE EXCLUSIVE BOYS' CLUB OF ENGLISH SCIENCE THROUGH BRILLIANCE AND DETERMINATION.

SHE HAD BECOME AN EXPERT IN X-RAY CRYSTALLOGRAPHY, A TECHNIQUE USED TO INFER THE STRUCTURE OF MOLECULES BASED ON THE PATTERNS OF SHADOWS CAST BY RADIATION STRIKING THEM.

MAN: IF YOU TAKE DNA, IT'S JUST LIKE PUTTING SALT INTO WATER.

AS THE WATER EVAPORATES, IT FORMS CRYSTALS, AND DNA BASICALLY DOES THE SAME THING, AND BY BOUNCING THE CRYSTALS BACK AND--WITH X-RAY FILM, THEY COULD, WITH QUITE COMPLICATED MATHEMATICS, WORK OUT THE SHAPE OF THE CRYSTAL.

NARRATOR: FRANKLIN WAS BASED IN THE SAME LAB AS MAURICE WILKINS, A SOFT-SPOKEN FORMER PHYSICIST FROM NEW ZEALAND, WHO HAD WORKED ON THE ATOM BOMB BEFORE TURNING TO BIOLOGY.

WILKINS ASSUMED THAT HIS YOUNGER COLLEAGUE WAS THERE MERELY TO ASSIST HIM, BUT FRANKLIN HAD OTHER IDEAS.

MUKHERJEE: ROSALIND FRANKLIN IS POWERFULLY DRIVEN BY THE IDEA OF SOLVING THIS STRUCTURE.

AND SHE LAUNCHES A SERIES OF EXPERIMENTS THAT ARE PROFOUND.

NARRATOR: FRANKLIN STRUNG STRANDS OF CRYSTALLIZED DNA ACROSS THE ENDS OF A PAPERCLIP, THEN BOMBARDED THE DNA WITH X-RAYS.

SHE TOOK PHOTO AFTER PHOTO, BUT EACH LACKED THE DETAIL NECESSARY TO DISCERN DNA'S HIDDEN STRUCTURE.

BUT FRANKLIN KEPT TRYING.

THEN, ON MAY 6, AFTER REFINING HER PROCESS, SHE ACHIEVED AN IMAGE SO CLEAR AND SYMMETRICAL THAT KEY PARTS OF THE MOLECULE'S STRUCTURE WERE UNMISTAKABLE.

SHE LABELED IT "PHOTOGRAPH 51."

LANDER: IT WAS BEAUTIFUL.

IT WAS PERFECT.

IT HAD INCREDIBLE CLARITY.

PHOTOGRAPH 51 HELD THE SECRET.

NARRATOR: A FEW MONTHS LATER, JAMES WATSON TRAVELED TO LONDON TO VISIT HIS FRIEND MAURICE WILKINS.

WITHOUT FRANKLIN'S PERMISSION, WILKINS SHOWED WATSON THE PRECIOUS PHOTO.

RIDLEY: AND IT'S WHEN THAT PICTURE GETS HANDED TO WILKINS, WHO SHOWS IT TO WATSON, THAT THE PENNY DROPS.

WATSON: IT WOULD MEAN THERE WAS A SIMPLE STRUCTURE.

JUST AS SIMPLE AS YOU CAN GET.

AND THAT'S ALL I LEARNED FROM MAURICE, AND, OF COURSE, I DIDN'T ASK HIM FOR THE PHOTOGRAPH, BUT I, OF COURSE, COULDN'T FORGET IT.

NARRATOR: HIS MIND REELING WITH THE IMPLICATIONS OF WHAT HE HAD SEEN, WATSON HURRIED TO KING'S CROSS STATION TO BOARD THE EVENING TRAIN BACK TO CAMBRIDGE.

AS THE TRAIN RACED ACROSS THE ENGLISH COUNTRYSIDE, WATSON SKETCHED THE INDELIBLE IMAGE IN THE MARGIN OF A PAGE TORN FROM A NEWSPAPER.

HE HAD NO DOUBT WHAT IT MEANT: THIS SPECIFIC SHADOW COULD ONLY HAVE BEEN MADE IF DNA WAS MADE UP OF TWO SPIRAL CHAINS COILED AROUND EACH OTHER: A SO-CALLED "DOUBLE HELIX."

BACK AT THE CAVENDISH, WATSON AND CRICK EXCITEDLY WENT TO WORK ON ANOTHER SET OF MODELS IN THE WINTER OF 1953, HOPING TO BUILD A DOUBLE HELIX THAT WOULD CHEMICALLY HOLD TOGETHER.

MUKHERJEE: WHAT THEY DO NEXT IS THAT THEY TRY TO SEE IF THEY CAN FIT A, C, T, G, AND, YOU KNOW, THE BACKBONE INTO A HELICAL STRUCTURE.

THEY TRY AND THEY FAIL.

AND THEY TRY AND THEY FAIL.

NARRATOR: BUT WATSON AND CRICK HAD ANOTHER IMPORTANT CLUE DISCOVERED BY A HUNGARIAN-BORN RESEARCHER AT COLUMBIA UNIVERSITY NAMED ERWIN CHARGAFF.

CHARGAFF LEARNED THAT THE NUMBER OF BASES IN DNA HINTED AT THEIR CONFIGURATION: Cs ALWAYS EQUALED Gs, AND Ts ALWAYS EQUALED As.

WATSON AND CRICK WONDERED IF THIS MEANT THEY MUST FIT TOGETHER IN PAIRS.

THEY HAD TRIED, AT ONE POINT OF TIME, TO MAKE THE BASES, THE A, C, T, G FACE OUTWARD.

AND THEY JUST COULDN'T JAM IT TOGETHER.

WHEN THEY MAKE THE BASES FACE INTO EACH OTHER, ALL OF A SUDDEN, THE WHOLE THING CLICKS.

NARRATOR: THE SOLUTION WAS SO STRAIGHTFORWARD, WATSON SAID, IT HAD TO BE CORRECT: A PERFECTLY SYMMETRICAL DOUBLE HELIX-- EACH STRAND THE MIRROR IMAGE OF THE OTHER, LIKE TEETH IN A ZIPPER.

LANDER: As FIT PERFECTLY WITH Ts TO MAKE A CERTAIN DISTANCE.

Cs FIT PERFECTLY WITH Gs TO MAKE EXACTLY THE SAME DISTANCE, SO THAT YOU COULD RUN A DOUBLE HELIX, AND THEY REALIZED, ON THIS DAY IN LATE FEBRUARY, THAT'S HOW INFORMATION WAS STORED.

IT WAS HOW IT WAS COPIED.

DNA HAD TWO COPIES.

EACH STRAND WAS A TEMPLATE FOR THE OTHER.

WATSON: IT WAS SO SIMPLE AND SO OBVIOUS.

WE'D FOUND THE SECRET OF LIFE: IT WAS.

THE SPECIFICITY OF LIFE: WHY, YOU KNOW, AN ANIMAL IS A COW AND WHY IT'S A GIRAFFE.

THAT'S DNA.

[APPLAUSE] NARRATOR: IN 1962, WATSON AND CRICK, ALONG WITH WILKINS, RECEIVED THE NOBEL PRIZE.

ROSALIND FRANKLIN, WHOSE PHOTOGRAPH HAD PROVIDED A KEY INSIGHT, HAD DIED OF OVARIAN CANCER 4 YEARS EARLIER-- HER CONTRIBUTION NEVER FULLY ACKNOWLEDGED.

LANDER: THE STRUCTURE OF DNA WAS THE SINGLE MOST REMARKABLE STRUCTURE EVER, BECAUSE IN ONE SIMPLE PICTURE, IT EXPLAINED EVERYTHING.

IT ANSWERS THE QUESTION: HOW DO WE STORE INFORMATION IN THE SEQUENCE OF LETTERS?

HOW DO WE REPLICATE INFORMATION?

WE PULL THOSE STRANDS APART AND EACH SERVES AS A TEMPLATE FOR THE OTHER.

SUDDENLY, EVERYTHING MAKES SENSE.

EVERYTHING ANYBODY HAD BEEN WONDERING ABOUT SINCE THEY FIRST NOTICED THAT CHILDREN LOOK LIKE THEIR PARENTS, EVERYTHING WAS INHERENT IN THAT ONE PICTURE.

IT WAS EXTRAORDINARY.

NARRATOR: THE SOLUTION TO THE STRUCTURE OF DNA ANSWERED MANY QUESTIONS, BUT ALSO RAISED NEW ONES.

IF DNA IS THE CODE, HOW IS IT TRANSLATED?

MAN: HOW DO WE GO FROM THIS ATG GGC CCC CCT OF DNA TO ACTIVE, VIBRANT LIVING MOLECULES CALLED PROTEINS?

NARRATOR: HOW DO WE GO FROM LETTERS TO LIFE?

IN THE YEARS FOLLOWING THE DISCOVERY OF THE STRUCTURE OF DNA, SCIENTISTS, INCLUDING WATSON AND CRICK THEMSELVES, GRADUALLY FILLED IN THE DETAILS.

DNA, IT TURNS OUT, IS THE MASTER COPY OF THE CODE ARCHIVED AWAY IN CHROMOSOMES.

IT NEEDS A WHOLE OTHER MOLECULE, ONE CALLED RIBONUCLEIC ACID, RNA, TO ACTUALLY COPY THE GENETIC INFORMATION AND USE IT TO MAKE FUNCTIONAL PROTEINS.

DNA IS, IN FACT, REALLY BORING.

IT DOESN'T DO ANYTHING.

JUST SITS THERE.

RNA MOLECULES DO STUFF.

THEY CAN COPY THEMSELVES, THEY CAN READ BITS OF DNA, AND RNA ACTUALLY MAKES THE PROTEIN.

SO RNA'S A REALLY, REALLY BUSY LITTLE MOLECULE.

DNA TO RNA TO PROTEIN.

BECAME KNOWN AS BIOLOGY'S CENTRAL DOGMA.

FURTHER DISCOVERIES BY SUCH SCIENTISTS AS SOUTH AFRICA'S SYDNEY BRENNER AND AMERICA'S MARSHALL NIRENBERG WOULD SHOW HOW TO ACTUALLY UNDERSTAND THE LANGUAGE IN WHICH THE DNA CODE IS WRITTEN.

SETS OF 3 BASES-- ATG, GAA, CTT-- CODE FOR 1 OF 21 DIFFERENT AMINO ACIDS.

THESE AMINO ACIDS IN THOUSANDS OF COMBINATIONS PRODUCE ALL THE PROTEINS IN OUR BODIES.

THE SYSTEM CAN BE THOUGHT OF AS LETTERS, WORDS, AND PARAGRAPHS-- BASES, AMINO ACIDS, AND PROTEINS.

10 OR 12 YEARS AFTER THE DOUBLE HELIX, YOU'VE ACTUALLY FINISHED THE STORY.

YOU'VE SAID WE'VE FOUND THE MEANING OF LIFE.

"MEANING OF LIFE" IS THAT 3-LETTER WORDS WRITTEN IN A 4-LETTER ALPHABET SPECIFY THE STRUCTURE OF PROTEINS IN EXACTLY THIS WAY.

I MEAN, HERE'S THE CIPHER BY WHICH WE DECODE THE GENETIC CODE.

AND REALLY, EVERY OTHER SPECULATION ABOUT WHETHER WE NEED QUANTUM PHYSICS OR WHETHER WE NEED MYSTICISM OR WHETHER WE NEED GOD SUDDENLY FALLS AWAY.

MUKHERJEE: REALLY BOGGLES THE BRAIN, HOW THIS SIMPLEST OF ALL MOLECULES, IN ONE SENSE, CAN CARRY THE MOST COMPLEX OF ALL INFORMATION IN THE WORLD.

IT DOES SO BY SEQUENCE, BECAUSE AGC CARRIES A DIFFERENT MESSAGE THAN ATC.

AND THIS CODE IS THE SAME ACROSS THE BIOLOGICAL WORLD.

THIS IS WHAT'S AMAZING ABOUT IT.

IT CONNECTS US TO EVERY ORGANISM THAT HAS EVER EXISTED, FROM BACTERIA, TO FLIES, TO ELEPHANTS, TO WHALES, TO HUMANS.

IT'S THE UNIVERSAL CODE OF LIFE ITSELF.

NRRRRR!

CHILD: I KNOW.

[ROSEN WHISTLING LIKE A BIRD] YEAH.

WELL, KEEP SINGING.

YOU DON'T HAVE TO STOP.

RRAAARRR!

NARRATOR: THOUGH THE ROSENS' TIRELESS WORK HAS MADE PROGRESS IN DRAWING VALUABLE ATTENTION TO THEIR DAUGHTER SUSANNAH'S ILLNESS, CALLED KIF1A... OK.

THEY ARE WORRIED THAT TIME IS RUNNING OUT.

WITH HER SEIZURES GETTING WORSE, LUKE ROSEN TAKES HER TO SEE HER NEUROLOGIST.

ROSEN: THE SEIZURE ELEMENT OF SUSANNAH'S DISEASE IS REALLY TERRIFYING AND REALLY MYSTERIOUS, AND IT'S NOT GETTING BETTER.

...BROWN HAIR, DR. ACHMED.

YES, DR. ACHMED HAS BROWN, SHORT HAIR.

ROSEN: IT'S BEEN REALLY HARD LATELY, BECAUSE THERE HAVE BEEN A COUPLE OF FAMILIES WHO'VE LOST THEIR KIDS.

BUT DID THE NURSE SAY IT?

WHAT DID THE NURSE SAY?

DO YOU WANT TO PUT IT ON SPEAKER PHONE?

ROSEN: LAST WEEK, THERE WAS A GIRL WHO DIED AFTER A SEIZURE.

♪ ...ON THE BUS GO... ♪ UM... SHH!

SHH!

SHH!

SHH, SHH, SHH, SHH, SHH, SHH.

♪ WHEELS ON THE BUS GO SHH, SHH, SHH ♪ ♪ ALL AROUND THE TOWN ♪ ♪ THE TOWN ♪ [TURN SIGNAL CLICKING] ♪ BABE, WE'RE HERE ♪ SUSANNAH: WE ARE HERE.

ROSEN: WE'RE HERE.

SO, IS ANYTHING NEW THAT I NEED TO KNOW?

UM, WELL, SHE'S NOT SLEEPING, REALLY.

SHE IS REALLY-- SHE'S EITHER, UM... NOT FALLING ASLEEP UNTIL, LIKE, 9:30 OR 10:00-- UH-HUH.

AND WAKING UP AT 4:30.

UH-HUH.

ROSEN: UM... THAT'S NEW.

YEAH, AND HER LEFT FOOT IS TURNED IN A LITTLE MORE.

AFTER THE LAST EEG, YOUR COLLEAGUE TOLD US THAT THERE WAS INCREASED ACTIVITY AT NIGHT.

ACTIVITY.

UH-HUH.

SO I'M KIND OF... YEAH, YEAH.

I DON'T KNOW...OK.

SO WE'LL TAKE A LOOK.

NARRATOR: GRADUALLY, THE KIF1A MUTATION HAS DESTROYED NEURONS IN SUSANNAH'S BRAIN, CAUSING HER CONDITION TO DETERIORATE.

WOMAN: LET'S SEE WHERE WE ARE.

SO THERE WAS ANY NEW INCIDENTS SINCE THE LAST TIME WE MET?

THE...HER TREMOR HAS--IS, UM... IS BETTER?

UH-UH.

NO.

NO?

NARRATOR: UNLESS THEY CAN TURN HOPE INTO AN ACTUAL TREATMENT, IT'S LIKELY SUSANNAH'S CONDITION WILL CONTINUE TO WORSEN.

ROSEN: SO I JUST TOOK THAT DURING THE EEG, BUT-- THOSE ARE HAPPENING.

WOMAN: WITH THE HAND?

YEAH.

YEAH, THE TREMOR, BUT ALSO, SHE'S, YOU KNOW... SPACING OUT.

MM-HMM.

ROSEN, ON VIDEO: HEY, SUS.

SUSANNAH, ON VIDEO: MM-HMM.

THIS IS A SHORTER ONE, AND WHEN SHE COMES OUT, YOU'LL SEE SHE...

DOES THAT.

SO NOTHING BAD.

WOMAN: OK, SO JUST ALMOST LIKE A-- A LITTLE SHAKE, KINDA.

WOMAN: MM-HMM.

I THINK THAT WAS PART OF HER SEIZURES.

YOU KNOW WHAT REALLY BOTHERS ME?

SHE SHOOK-- YEAH.

AND THEN ALMOST LIKE A SNAP OUT OF IT.

YEAH.

IT MAKES ME FEEL THAT WE TALK ABOUT MAYBE THAT SHE HAS ABSENCE SEIZURES.

YEAH, YEAH.

AND ONCE THAT ACTIVITY IS OVER, THEN SHE'S BOUNCED BACK TO HER BASELINE.

OK. CHUNG: WITH SUSANNAH, THERE HAD BEEN WHAT WE CALL ATROPHY.

PUT BOTH HANDS UP.

VERY GOOD.

THIS IS PROGRESSING AT A RELATIVELY RAPID RATE.

SO IT BECOMES INCREASINGLY URGENT.

WE HAVE TO BE THE SOLUTION OURSELVES, AND WE NEED TO DO THIS TODAY.

[TALKING INDISTINCTLY] ROSEN: EVERY MOMENT WITH HER IS PRECIOUS AND POSSIBLY FLEETING.

ARE YOU--DR. ACHMED'S HAND?

MY HAND?

LET'S DO IT.

DR. ACHMED'S BUSY.

ALL RIGHT, BYE!

BYE, SUSIE.

THANK YOU.

ROSEN: THE IDEA THAT THERE COULD BE A POINT IN TIME WHERE THIS MUTATION IS GOING TO KICK INTO GEAR AND SHE'S JUST NOT GONNA KNOW WHO I AM...

YES, YOU CAN DEFINITELY HAVE A LOLLIPOP.

THAT'S TERRIFYING.

NOW WE'RE MOVING FASTER.

WHOOPS.

HOLD ON.

CHUNG: IT IS A BRAND-NEW WORLD.

GOOD GIRL.

THE QUESTION IS, CAN WE MAKE IT A BRAND-NEW WORLD IN TIME FOR SUSANNAH.

NARRATOR: WITH THE DISCOVERIES OF DNA'S STRUCTURE AND FUNCTION IN THE 1950s AND 1960s, ITS KEY ROLE IN THE CREATION OF LIFE BECAME CLEAR.

BUT WHAT ROLE DID DNA AND THE GENES IT CONTAINS PLAY IN ILLNESS AND DEATH?

THE CONNECTION BETWEEN GENES AND DISEASE HAD LONG BEEN SUSPECTED, BUT EXACTLY WHAT GENES WERE INVOLVED AND WHERE TO FIND THEM WAS STILL LARGELY A MYSTERY.

[HORNS HONKING] EARLY ONE MORNING, IN 1968, LEONORE WEXLER, A 52-YEAR-OLD MOTHER OF TWO, ARRIVED FOR JURY DUTY IN DOWNTOWN LOS ANGELES.

AS SHE CROSSED THE STREET TO THE COURTHOUSE, SHE WALKED ERRATICALLY AND SEEMED DISORIENTED.

WOMAN: THE POLICEMAN JUST SCREAMED AT HER AT THE TOP OF HIS LUNGS, "HOW CAN YOU BE DRUNK SO EARLY IN THE MORNING?

AREN'T YOU ASHAMED OF YOURSELF?"

WOMAN: SHE CALLED MY DAD, AND HE TRIED TO CALM HER DOWN.

NANCY: MY DAD SAID, "JUST COME HOME "AND I'LL HAVE A DOCTOR SEE YOU AND SEE WHAT HE THINKS."

WHEN THE DOCTOR EXAMINED HER, SHE HAD CLEAR SIGNS OF HUNTINGTON'S.

NARRATOR: FIRST DESCRIBED IN 1872, HUNTINGTON'S DISEASE IS RARE, PROGRESSIVE, AND INEVITABLY FATAL.

PATIENTS FIRST EXPERIENCE SMALL TREMORS AND FORGETFULNESS, BUT EVENTUALLY LOSE THEIR ABILITY TO WALK, TALK, AND FEED THEMSELVES.

AS THEIR MINDS AND ORGANS DETERIORATE, DEATH USUALLY COMES MERCIFULLY FROM A WEAKENED HEART OR LUNGS.

FOR LEONORE WEXLER, IT WAS A DIAGNOSIS SHE HAD BEEN DREADING SINCE SHE WAS A GIRL, WHEN SHE'D BEEN TOLD THAT HER FATHER HAD DIED OF THE DISEASE-- THE SAME DISEASE THAT LATER TOOK ALL 3 OF HER BROTHERS.

WHEN LEONORE HERSELF WAS DIAGNOSED, HER HUSBAND MILTON DECIDED HE COULD NO LONGER HIDE THE FAMILY SECRET FROM HIS OWN DAUGHTERS.

HE EXPLAINED TO ALICE AND NANCY THAT HUNTINGTON'S IS CAUSED BY A MUTATION IN A DOMINANT GENE.

IF THEY HAD INHERITED THAT GENE FROM LEONORE, THEY, TOO, WOULD DEVELOP THE DISEASE.

ALICE: HE SAID, "YOU KNOW, YOU EACH HAVE A 50-50 CHANCE OF GETTING IT.

"AND IF YOU HAVE CHILDREN "AND THEN YOU LATER DEVELOP THE DISEASE, THEY WILL EACH HAVE A 50-50 CHANCE AS WELL."

NANCY: WE WERE JUST HOLDING ONTO EACH OTHER.

WE WERE SOBBING.

AND YOU THINK, "OH, MY GOD," YOU KNOW.

EVERYTHING THAT YOU PLANNED FOR YOUR LIFE IS JUST TOTALLY SHATTERED TO PIECES, YOU KNOW.

HOW DO WE LIVE?

HOW DO WE PUT ONE STEP IN FRONT OF THE OTHER, YOU KNOW, AND ACT NORMAL?

NARRATOR: ON MAY 14, 1978, 10 YEARS AFTER HER DIAGNOSIS, LEONORE WEXLER FINALLY SUCCUMBED TO HER DISEASE.

NANCY: HER SUFFERING WAS JUST HORRIFIC, YOU KNOW.

SHE WAS JUST MOVING CONSTANTLY, AND THEY WOULD LITERALLY TIE HER UP 'CAUSE SHE WAS MOVING ALL THE TIME.

BUT WHEN SHE PASSED AWAY, HOLDING HER HAND-- SHE HAD VERY BEAUTIFUL HANDS.

YOU KNOW, HER HANDS WERE, LIKE, STILL FOR THE FIRST TIME.

NARRATOR: BECAUSE HUNTINGTON'S USUALLY STRIKES LATER IN LIFE, NANCY AND ALICE STILL DIDN'T KNOW IF THEY HAD THE MUTATED GENE.

NANCY DECIDED SHE WOULD NOT WAIT TO FIND OUT.

WITH NEXT TO NO TRAINING IN GENETICS, SHE DECIDED TO GO IN SEARCH OF THE GENE HERSELF.

I'M NOT VERY GOOD AT SORT OF LIVING PASSIVELY OR LIVING WITH AMBIGUITY.

I'D RATHER, YOU KNOW, GO GET, RATHER THAN WAIT FOR SOMETHING TO GET ME.

I THOUGHT IF I CAN FIND THE GENE AND FIX THE GENE THAT WOULD BE THE CURE.

NARRATOR: THE SCALE OF THE CHALLENGE WAS ENORMOUS.

NO ONE HAD EVER FOUND A SPECIFIC DISEASE GENE BEFORE, LET ALONE REPAIRED ONE.

NANCY: WHEN YOU THINK ABOUT THE TOOLS BACK THEN, YOU KNOW, THERE WEREN'T ANY.

TO ACTUALLY THINK YOU'RE GONNA BE A GENE HUNTER AND GO FIND A GENE, FORGET IT.

I MEAN, IT WAS JUST IMPOSSIBLE.

MAN: IF YOU'RE INITIALLY TRYING TO FIND A GENE THAT CAUSES A PARTICULAR DISEASE AND NOT JUST THE GENE BUT THE MISSPELLING IN THAT GENE THAT'S RESPONSIBLE, THAT'S A NEEDLE IN THE HAYSTACK.

OR YOU COULD THINK OF IT IN GEOGRAPHIC TERMS.

IT'S LIKE TRYING TO FIND A SINGLE BURNED-OUT LIGHT BULB IN A BASEMENT OF A HOUSE SOMEWHERE IN THE UNITED STATES.

NARRATOR: BUT WHAT IF IT WERE POSSIBLE TO NARROW DOWN THE SEARCH TO A SINGLE NEIGHBORHOOD ON THE DNA MOLECULE?

A RESEARCHER AT MIT NAMED DR. DAVID BOTSTEIN WAS TRYING TO DO JUST THAT USING THE TECHNIQUE OF LINKAGE, DETERMINING THE RELATIVE LOCATION OF GENES BASED ON PATTERNS OF INHERITANCE.

LANDER: DAVID BOTSTEIN HAD A BRILLIANT INSIGHT.

HE REALIZED, "WE COULD TRACE THE GENE "THAT'S CAUSING A HUMAN DISEASE "AS LONG AS WE HAD SOME OTHER GENETIC DIFFERENCE TO FOLLOW ITS TRANSMISSION IN FAMILIES."

IN FRUIT FLIES, YOU'D USE CURLY WINGS AND WHITE EYES, BUT YOU CAN'T DO THAT FOR HUMANS.

BUT BOTSTEIN REALIZED THERE WAS ONE THING YOU COULD USE.

TRIVIAL GENETIC SPELLING DIFFERENCES.

MAN: THERE ARE 3 BILLION BASES OF DNA AT ANY GIVEN LOCATION ON A CHROMOSOME.

PEOPLE ARE MOSTLY THE SAME.

BUT EVERY ONCE IN A WHILE, EVERY 500 TO 1,000 OF THESE BASES, THERE'S A DIFFERENCE.

AS SOON AS YOU GET THAT ONE DIFFERENCE, YOU CAN FOLLOW THAT.

NARRATOR: THESE SMALL, HARMLESS SPELLING DIFFERENCES IN HUMAN DNA WERE KNOWN AS MARKERS.

MAN: A MARKER IS SIMPLY A SIGNPOST THAT ALLOWS YOU TO TRACK THAT BIT OF DNA AS IT'S PASSED ON THROUGH THE GENERATIONS.

NARRATOR: IN PATIENTS WITH HUNTINGTON'S, THE THEORY WENT, MARKERS WOULD POINT RIGHT TO THE AREA WHERE THE ABERRANT GENE IS LOCATED.

NANCY WEXLER STUDIED BOTSTEIN'S IDEAS WITH GROWING EXCITEMENT.

NANCY: IT WAS SO PREMATURE.

NOBODY WAS DOING IT.

NOBODY WAS THINKING ABOUT IT.

NOBODY WAS PUBLISHING IT.

BUT EVERYBODY WAS SORT OF TALKING ABOUT IT AS A POSSIBILITY.

MAYBE YOU COULD ACTUALLY TAKE THIS NEXT STEP.

YOU KNOW, USE THESE MARKERS TO ACTUALLY FIND THE HUNTINGTON'S GENE.

MUKHERJEE: HER QUEST BECOMES A MEDICAL DETECTIVE STORY 'CAUSE IT MOVES FROM THE ABSTRACT SPACE OF THE HUMAN GENOME, A REAL PLACE WHERE THE GENE MIGHT BE FOUND.

AND THROUGH SHEER FORCE OF PERSONALITY, SHE BRINGS TOGETHER A CONSORTIUM OF SCIENTISTS TO CRACK THE GENETIC MYSTERY OF HUNTINGTON'S DISEASE.

NARRATOR: AS WEXLER AND HER TEAM BEGAN THEIR WORK, ONLY A DOZEN MARKERS HAD YET BEEN IDENTIFIED.

THE SCARCITY OF MARKERS WAS ONLY ONE PROBLEM.

WEXLER NEEDED A FAMILY OF HUNTINGTON'S PATIENTS LARGE ENOUGH TO TRACK THE RELATIONSHIP BETWEEN MARKERS AND DISEASE.

WEXLER SEARCHED FOR YEARS BUT COULD FIND NO FAMILY WITH ENOUGH GENERATIONS OF HUNTINGTON'S PATIENTS TO ESTABLISH A MEANINGFUL PATTERN.

THEN, SHE LEARNED OF THE EXISTENCE OF A UNIQUE CLUSTER OF HUNTINGTON'S PATIENTS SAID TO BE LIVING IN A TOWN ON THE SHORE OF LAKE MARACAIBO, VENEZUELA.

IN 1979, THEY SET OUT TO FIND THIS RAREST OF COMMUNITIES.

WOMAN: WE COULD SEE PEOPLE WHO WERE OUT IN THE STREETS THAT CLEARLY HAD HUNTINGTON'S.

I'D LOOK DOWN THE STREET, THERE WAS SOMEBODY ELSE AND SOMEBODY ELSE.

AND IT WAS LIKE THE WHOLE TOWN.

YOU KNOW, THERE WAS SOMEBODY IN EVERY FAMILY THAT HAD IT.

NARRATOR: AS SHE INTERVIEWED VILLAGERS, WEXLER AND HER TEAM ASKED IF THEY KNEW OF ANY FAMILY THAT HAD BEEN HIT PARTICULARLY HARD BY HUNTINGTON'S.

THEY WERE TOLD OF A SINGLE, LARGE FAMILY LIVING IN STILT HUTS ON A REMOTE PART OF THE LAKE EKING OUT A LIVING CATCHING FISH.

NANCY: WE MEANDERED RIGHT INTO THE HEART OF THIS LITTLE STILT VILLAGE.

AND IN EVERY SINGLE HOUSE, THERE WAS SOMEBODY WITH HUNTINGTON'S.

IN ONE HOUSE, THERE WAS A LITTLE OLD LADY CLEANING FISH, HER BROTHER LIVING RIGHT NEXT DOOR.

HE WAS ROCKING BACK AND FORTH IN A HAMMOCK, AND HE CLEARLY HAD HUNTINGTON'S.

WE SAID, "YOU KNOW, WHERE'S YOUR WIFE?"

AND HE POINTED ACROSS THE WAY TO HIS WIFE, WHO ALSO ROCKING BACK AND FORTH.

AND THEN I SAID, YOU KNOW, "BUT HOW MANY KIDS DO YOU HAVE?"

THEY HAVE 14 LIVING KIDS.

ONE OF THEIR DAUGHTERS ALREADY HAD HUNTINGTON'S, YOU KNOW, AT A YOUNG AGE.

THE PEOPLE--I THINK, FIRST OF ALL, THEY WERE SURPRISED BY ME, YOU KNOW, "WHAT ARE YOU DOING HERE?"

AND SO I TRIED TO EXPLAIN THAT MY MOM HAD THE SAME DISEASE.

SO I SAID, "MY FAMILY AND YOUR FAMILY ARE RELATED.

"AND I'M LOOKING FOR A BIG FAMILY.

"AND YOU REALLY HAVE THE BIGGEST FAMILY IN THE WORLD, AND WE NEED YOUR HELP."

[SPEAKING SPANISH] NARRATOR: WEXLER'S TEAM SET UP A CLINIC AND BEGAN IDENTIFYING THE HUNTINGTON'S CARRIERS.

GRADUALLY, SHE BUILT A VAST FAMILY TREE, TRACKING THE GENETIC DISORDER ACROSS MULTIPLE GENERATIONS.

MUKHERJEE: WHAT'S ASTONISHING ABOUT NANCY WEXLER'S QUEST IS THAT SHE FUNNELS ALL OF GENETICS-- MENDEL'S IDEAS ABOUT DOMINANT AND RECESSIVE FACTORS, MORGAN'S IDEA OF LINKAGE, GENETIC MAPPING-- SHE TAKES ALL OF THIS, AND SHE DISTILLS IT DOWN TO THE QUEST TO FIND THAT ONE GENE THAT CAUSES THE DISEASE THAT RUNS IN HER FAMILY.

[WEXLER SPEAKING SPANISH] NARRATOR: OVER THE COURSE OF 2 WEEKS, WEXLER AND HER TEAM DREW BLOOD AND SKIN SAMPLES FROM EVERY FAMILY MEMBER THEY COULD FIND.

[CHILD CRYING] THEY SHIPPED THE SAMPLES BACK TO BOSTON, HOPING TO FIND A CORRELATION BETWEEN THOSE VILLAGERS WITH THE DISEASE AND SOME COMMON SPELLING VARIATION IN THEIR DNA.

GUSELLA: OUR GOAL WAS: FIND THE MARKER THAT TRACKED WITH HUNTINGTON'S DISEASE, NOT BECAUSE IT CAUSED HUNTINGTON'S DISEASE BUT BECAUSE IT WAS NEAR THE SAME LOCATION.

IN THE BEGINNING, MOST PEOPLE DIDN'T REALLY BELIEVE IT WAS GONNA WORK VERY QUICKLY.

AND AS A MATTER OF FACT, WHEN OUR GRANT WAS INITIALLY REVIEWED, THERE WERE PEOPLE ON THE REVIEW PANEL WHO SAID, "THIS'LL TAKE 50 YEARS."

COLLINS: THE FIRST GROUP THAT JIM GUSELLA TRIED-- AND IT SHOULD HAVE TAKEN HUNDREDS BEFORE HE WAS IN THE RIGHT PLACE-- SHOWED CLEAR, 1,000 TO 1 PLUS EVIDENCE OF BEING LINKED TO THE HUNTINGTON'S DISEASE GENE.

NARRATOR: TO CONFIRM HIS ASTONISHING FINDINGS, GUSELLA REVIEWED THE RESULTS OF TESTS ALREADY DONE ON A SMALLER AMERICAN FAMILY THAT ALSO HAD HUNTINGTON'S.

THEY HAD EXACTLY THE SAME MARKER, THE SAME SPELLING VARIATION IN THEIR DNA DISCOVERED IN THE VENEZUELANS.

[BEEP] NANCY: JIM CALLED ME, AND I WAS AT A RESTAURANT.

I SAID--AND I JUST...

I STARTED SCREAMING, YOU KNOW, "WHAT?"

YOU KNOW, "YOU FOUND IT!

YOU FOUND IT!

YOU FOUND IT!

SCREAMING, SCREAMING, SCREAMING.

THIS IS THE FIRST TIME IN HISTORY WHEN YOU COULD ACTUALLY FIND A MARKER THAT WAS SITTING EXTREMELY CLOSE TO A DISEASED GENE ON A HUMAN CHROMOSOME.

GUSELLA: SHE WAS, YOU KNOW, OVER THE MOON.

IT WAS REALLY-- I MEAN, THIS WAS THE WHOLE GOAL OF THE ENTIRE THING.

IT WAS REALLY A FANTASTIC FEELING.

NARRATOR: WHEN SCIENTISTS FINALLY FOUND THE MUTATED GENE RESPONSIBLE FOR HUNTINGTON'S NEAR THE MARKER ON CHROMOSOME 4, THEY DISCOVERED THAT IT CONTAINED A CHEMICAL PHRASE CAG REPEATING LIKE A STUTTER IN THE GENETIC CODE.

THE EXTRA PROTEIN PRODUCED AS A RESULT GRADUALLY DESTROYS NEURONS IN THE BRAIN, LEADING TO HUNTINGTON'S SYMPTOMS.

DOCTORS STILL HAD NO WAY TO TREAT THE DISEASE, BUT NOW THEY COULD TEST FOR IT.

WHETHER OR NOT TO TAKE THE TEST TO GLIMPSE THEIR FUTURES RAISED HARROWING QUESTIONS FOR THE WEXLERS AND NEARLY EVERY OTHER HUNTINGTON'S FAMILY.

FOR NANCY WEXLER, THE DECISION WAS CLEAR.

NANCY: FOR MYSELF, PERSONALLY, I DECIDED NOT TO GET TESTED UNTIL THERE'S SOMETHING THAT COULD ACTUALLY MAKE A DIFFERENCE IN TERMS OF TREATMENT.

IF THE SCIENCE CHANGED, THEN I WOULD RECONSIDER.

LIVING WITH AMBIGUITY IS VERY EXHAUSTING.

LIVING WITH CERTAINTY THAT I WAS GONNA DIE I THINK, TO ME, WOULD BE A LOT MORE HORRIFIC.

I DON'T THINK I COULD DO THAT, YOU KNOW, AND STILL BE FUNCTIONAL.

SO I'D RATHER LIVE WITH THE AMBIGUITY.

[PEOPLE ALL TALKING AT ONCE] NARRATOR: THE ALLENS ARE A LARGE FAMILY IN THE UNITED KINGDOM LIVING WITH HUNTINGTON'S.

3 SIBLINGS HAVE THE DISEASE-- PETER, FRANK, AND SANDY.

WOMAN: I THINK HE COULD HAVE GONE ON.

NARRATOR: THEY HAVE 8 CHILDREN AMONG THEM, EACH OF WHOM IS AT RISK AND MUST DECIDE WHETHER TO GET TESTED FOR THE GENETIC MUTATION.

MAN: BY THE WAY.

NARRATOR: THE ALLENS ILLUSTRATE THE DILEMMA PATIENTS FACE IN THE GAP BETWEEN DIAGNOSIS AND CURE.

JENNY, SANDY'S ELDEST DAUGHTER, HAS RECENTLY DECIDED TO TAKE THE TEST FOR HUNTINGTON'S.

JENNY: I JUST COULDN'T HAVE THE QUESTION PLAYING ON MY MIND FOR THE REST OF MY LIFE WHETHER I DO OR I DON'T.

I JUST FEEL LIKE I NEED TO... JUST NEED TO KNOW.

YOU KNOW, IF I FIND OUT I DON'T HAVE IT, IT'S NOT LIKE I CAN JUST BE LIKE, "OK, ALL RIGHT.

I DON'T HAVE TO THINK ABOUT HUNTINGTON'S EVER AGAIN."

IT'S, YOU KNOW--IT'S STILL GONNA BE A MASSIVE PART OF MY LIFE WITH MUM AND THEN WITH WHATEVER RESULTS MY SISTERS AND MY COUSINS HAVE.

HI.

NICE TO SEE YOU.

HI.

JENNY: SO, I'VE WANTED TO DO IT FOR QUITE A FEW YEARS NOW, ABOUT 3 YEARS, AND I'VE KIND OF HAD IT ON MY MIND FOR ALL THAT TIME.

KIND OF, I DEFINITELY WANTED TO GET TESTED, BUT JUST VARIOUS THINGS WITHIN MY FAMILY AND WANTING IT TO BE THE RIGHT TIME FOR THE WHOLE FAMILY OF MY SISTERS AND STUFF, I'VE WAITED TILL NOW TO DO IT.

SO, JENNY, TELL ME ABOUT WHEN YOU FIRST LEARNED ABOUT THE HISTORY OF HUNTINGTON'S DISEASE IN YOUR FAMILY.

I WAS IN A SCIENCE LESSON AT SCHOOL.

AND I--WE WERE LEARNING ABOUT HUNTINGTON'S.

I KNEW THAT MY GRAN HAD IT, BUT I DIDN'T KNOW-- HADN'T REALLY ASKED LOADS OF QUESTIONS.

I KIND OF JUST KNEW SHE WAS ILL.

BUT THEY TALKED ABOUT HOW IT WAS GENETIC, IT'S PASSED ON TO THEIR CHILDREN.

AND I PUT MY HAND UP AND SAID, "WELL, MY GRAN HAS THAT, AND MY MUM'S NEVER SAID ANYTHING ABOUT THAT."

AND SO MY TEACHER JUST SAID, "OH, SHE PROBABLY-- "THERE'S NOTHING TO WORRY ABOUT THEN.

YOU KNOW, SHE PROBABLY DOESN'T HAVE IT."

AND THAT NIGHT, I WENT HOME AND OBVIOUSLY ASKED MY PARENTS ABOUT IT.

AND THEY'D BEEN WAITING FOR ME TO ASK THE QUESTION, BASICALLY.

THAT WAS THEIR DECISION, THAT THEY'D SAID THEY WOULD TALK TO ME ABOUT HUNTINGTON'S WHENEVER I ASKED.

NARRATOR: JENNY IS THE FIRST OF 8 IN HER GENERATION OF THE ALLEN FAMILY TO BE TESTED.

SHE WILL FIND OUT THE RESULTS IN ABOUT 4 WEEKS.

JENNY: I FEEL LIKE I'VE GOT THE BIG WEIGHT ON ME TO, LIKE, DO THIS RIGHT IN A WAY.

AND I DON'T KNOW HOW--I DON'T KNOW WHAT DOING IT RIGHT MEANS, BUT LIKE DO IT RIGHT AND SHOW THEM THAT IT'S NOT SCARY AND THAT YOU CAN GET THROUGH IT AND...

WHICH--WHICH IS TOUGH.

NARRATOR: BY THE 1980s, THE GENETIC CODE HAD BEGUN TO YIELD SOME OF ITS DEEPEST SECRETS.

FINDING THE GENES FOR DISEASES LIKE HUNTINGTON'S AND UNDERSTANDING HOW THEY ARE DAMAGED WERE IMPORTANT BREAKTHROUGHS, BUT ACTUAL CURES WOULD REQUIRE BOLD NEW APPROACHES, INCLUDING THE BOLDEST OF ALL-- EDITING THE DNA CODE ITSELF.

MUKHERJEE: WE UNDERSTOOD THE WORLD OF GENES IN SOME FUNDAMENTAL WAYS.

WE KNEW THE STRUCTURE OF DNA.

WE KNOW THAT ASPECTS OF OUR LIVES THAT ARE RANDOM OR COINCIDENTAL TURN OUT TO HAVE AT LEAST SOME UNDERLYING GENETIC COMPONENTS, AND THEN WE'VE BEGUN TO SEE THAT ALTERATIONS IN GENES CAN CAUSE DISEASE.

THE QUESTION WAS: NOW THAT YOU KNOW ALL THIS INFORMATION ABOUT DNA, CAN YOU CHANGE IT, NOT WAIT FOR EVOLUTION TO DO IT, BUT COULD YOU DO IT?

COULD HUMAN BEINGS DO IT?

NARRATOR: THE IDEA OF EDITING HUMAN DNA EVOKED SOME OF THE DARKEST PERIODS OF THE 20th CENTURY, WHEN EARLY ENTHUSIASM FOR EUGENICS DEVOLVED INTO GENOCIDE.

MUKHERJEE: THIS GOES BACK TO AN OLD QUESTION: CAN YOU MAKE HUMAN GENOMES BETTER AND AVOID DISEASE?

OR WILL THAT BE CORRUPTED BY THE DESIRE TO MAKE HUMAN GENOMES BETTER TO MAKE BETTER HUMANS?

IT'S AN OLD QUESTION, AND IT'S A NEW QUESTION.

NARRATOR: BY THE LATE 1970s, THE NOTION OF REACHING RIGHT INTO THE CELL AND DIRECTLY MANIPULATING DNA WAS NO LONGER A PIPE DREAM.

IN FACT, SCIENTISTS HAD DISCOVERED THAT ONE ORGANISM, BACTERIA, WAS ALREADY DOING IT.

ONE OF THE OLDEST LIFE FORMS ON EARTH, BACTERIA HAD EVOLVED ENZYMES CAPABLE OF CUTTING THE DNA OF INVADING VIRUSES INTO HARMLESS PIECES.

WE KNOW NOW THAT THE 3-DIMENSIONAL STRUCTURE AND... NARRATOR: PAUL BERG, A BIOCHEMIST AT STANFORD, CONCEIVED A SERIES OF BOLD EXPERIMENTS.

COULD HE WIELD THESE SAME BACTERIAL SCISSORS INTENTIONALLY TO CREATE A GAP IN A PIECE OF VIRAL DNA?

THEN COULD HE STITCH TOGETHER THAT GAP WITH DNA FROM THE BACTERIA?

IN OTHER WORDS, COULD DNA FROM TWO DIFFERENT LIFE FORMS BE COMBINED?

BERG'S EXPERIMENT, REALLY, WAS TO ASK THE QUESTION: IF YOU USE THESE TOOLS IN SEQUENCE, IF YOU CUT AND IF YOU THEN PASTE IT, WOULD YOU GET A HYBRID WHICH WOULD CONTAIN GENETIC INFORMATION FROM TWO DIFFERENT SPECIES OF ORGANISMS?

THE IDEA, BEING ABLE TO INTRODUCE NEW DNA INTO EXISTING CELLS THAT COULD ALTER THEIR GENETIC BEHAVIOR WAS CLEARLY A FIRST.

NOBODY HAD DONE THAT BEFORE.

WE HAD IN OUR REFRIGERATOR ALL THE ENZYMES THAT WERE NEEDED, AND WE JUST SET OUT TO ACTUALLY DO IT.

NARRATOR: BERG'S ATTEMPT TO FUSE THE DNA OF TWO DIFFERENT SPECIES WAS NO MERE FRANKENSTEIN EXPERIMENT.

IF HE COULD SUCCESSFULLY SPLICE TOGETHER DNA IN SIMPLE ORGANISMS, HE MIGHT BE ABLE TO DO IT IN HIGHER ORGANISMS AS WELL WITH PROFOUND MEDICAL AND ETHICAL IMPLICATIONS.

BY OCTOBER, 1971, BERG HAD DONE IT.

THE VIRUS HYBRID HE HAD CREATED WAS VIABLE.

LIKE ANY WRITTEN LANGUAGE, DNA COULD BE CUT, COPIED, AND PASTED EVEN BETWEEN TWO DIFFERENT SPECIES.

BERG CALLED IT RECOMBINANT DNA.

WOMAN: THE BEAUTY OF DNA, THE THING THAT I ALWAYS FIND AMAZING, IS IT'S EXACTLY THE SAME FOR ALL LIFE FORMS.

THE Gs AND As AND Ts AND Cs WORK IN EVERYTHING FROM A VIRUS UP TO A HUMAN.

AND IF THAT WEREN'T TRUE, WE COULDN'T TAKE CODE FROM ONE ORGANISM AND PUT IT INTO ANOTHER.

NARRATOR: ALTHOUGH THE NEW TECHNOLOGY REPRESENTED ONLY A FIRST STEP TOWARD MANIPULATING DNA IN HUMANS, IT WAS IMMEDIATELY RECOGNIZED AS A HUGE ADVANCE.

MAN: IT'S HARD TO DESCRIBE HOW QUICKLY THIS ALL HAPPENED.

IT WAS NOT VERY LONG BEFORE THAT ALL OF THESE QUESTIONS ABOUT "HOW DOES LIFE WORK?"

WERE COMPLETELY MYSTERIOUS, HADN'T REALLY CHANGED FOR THOUSANDS OF YEARS.

AND SUDDENLY, NOT ONLY DO WE HAVE THE ANSWERS, BUT WE SWITCHED FROM BEING ONLY SCIENTISTS TO BEING ENGINEERS, AND GENETIC ENGINEERING BEGAN.

AND THERE WAS SOMETHING BEAUTIFUL, FRIGHTENING, AMAZING ABOUT THAT BECAUSE WE SUDDENLY HAD THE POWER THAT PREVIOUSLY HAD BELONGED TO EVOLUTION ITSELF.

NARRATOR: THE EXCITEMENT OVER GENETIC ENGINEERING SWEPT THE FIELD, BUT FOR SOME THE NEW TECHNOLOGY CONJURED UP FRIGHTENING ASSOCIATIONS.

MEDDLING WITH HEREDITY COULD UNLEASH POWERFUL, POSSIBLY UNCONTROLLABLE FORCES.

LANDER: MOLECULAR BIOLOGISTS HAD A REAL RECKONING.

THEY HAD TO STOP AND ASK, "HOW DO WE GO FORWARD?

"DO WE GO FORWARD AT ALL?

"DO WE GO FORWARD WITH SOME PRETTY TIGHT RULES?

"IF WE SHUT IT ALL DOWN, WE'LL NEVER REALIZE THE PROMISE.

"AND IF WE DON'T TAKE IT SERIOUSLY, "WELL, HOW ARE WE GONNA EXPLAIN IT TO OUR KIDS IF SOMETHING GOES SERIOUSLY WRONG?"

CAPLAN: THIS IS SCARING A LOT OF PEOPLE.

THERE ARE THOSE THAT SAY, "LOOK, WE DON'T KNOW WHAT "THEY'RE GONNA BE ENGINEERING HERE, "AND THIS IS NOT A GOOD DIRECTION TO GO IN.

"IT MAY NOT BE SAFE.

"WE THINK A LOT OF THIS MOLECULAR ENGINEERING SHOULD STOP."

NARRATOR: INITIALLY, BERG DISMISSED THESE FEARS, BUT THE MORE HE HEARD ABOUT HOW HIS TECHNIQUES COULD BE USED IN RISKY EXPERIMENTS, THE MORE HIS CONCERN GREW.

BERG: I BEGAN TO THINK HARD ABOUT IT.

I WENT--TRAVELED AROUND THE COUNTRY AND SAMPLED PEOPLE'S OPINIONS, EXPERTS' OPINIONS, AND NOBODY COULD SAY THE PROBABILITY OF THAT HAPPENING WAS ZERO.

NARRATOR: WITH THE MEDIA TRACKING PUBLIC FEARS ABOUT BIOLOGICAL EXPERIMENTATION, BERG CALLED ON SCIENTISTS TO RESPECT AN IMMEDIATE MORATORIUM ON ALL FURTHER RECOMBINANT DNA EXPERIMENTS UNTIL THE RISKS WERE BETTER UNDERSTOOD.

BERG, ON VIDEO: WE'RE WORRIED ABOUT SOME OF THESE EXPERIMENTS.

ARE THERE RISKS, AND IF THERE ARE, WHAT DO WE DO ABOUT THEM?

MUKHERJEE: WHAT IS GOING THROUGH PAUL BERG'S MIND AND THE MINDS OF OTHER SCIENTISTS IS THAT MAYBE THE RISK IS NEGLIGIBLE...

BUT ARE THEY SURE IT'S ZERO?

AND IF IT'S NOT ZERO, THEN WE HAVE TO PAUSE BEFORE MOVING FORWARD.

NARRATOR: WITH MORE AND MORE SCIENTISTS EAGER TO PUT THIS POWERFUL NEW TECHNOLOGY TO USE, BERG CONVENED A CONFERENCE OF LEADING GENETICISTS, ETHICISTS, JOURNALISTS, AND LAWYERS AT A RUSTIC RESORT NEAR SAN FRANCISCO CALLED ASILOMAR.

COBB: THEY HAD A BIG MEETING, WHICH IS OFTEN CALLED "THE WOODSTOCK OF SCIENCE," THEY CAME UP WITH A SET OF CONTAINMENT CRITERIA FOR BIOSECURITY TO ENSURE THAT THERE WAS NO DANGER FOR PEOPLE USING THESE SYSTEMS.

BERG: AND AFTER 2 1/2 DAYS, THE RECOMMENDATION WAS TO DEVELOP GUIDELINES, WHICH THEY DID.

AND A YEAR LATER, THESE GUIDELINES WERE PROMULGATED, AND ESSENTIALLY WHAT THEY DID IS SET THE STAGE FOR HOW PEOPLE COULD DO RECOMBINANT DNA RESEARCH.

CAPLAN: AND THEY BASICALLY SAID, "YOU CAN TRUST US, "'CAUSE WE'RE GONNA LAY OUT CONDITIONS-- CONTAINMENT, SAFETY-- "THAT ARE GONNA MAKE SURE WE CAN PROCEED IN A SAFE MANNER WITH OUR MOLECULAR ENGINEERING."

NARRATOR: BUT MANY IN THE PUBLIC DID NOT TRUST SCIENTISTS TO POLICE THEMSELVES.

THE CONTROVERSY REACHED A FLASHPOINT WHEN HARVARD AND MIT BROKE GROUND ON NEW BIOSAFETY LABORATORIES, WHERE SCIENTISTS PROMISED THEY WOULD CARRY OUT RECOMBINANT DNA RESEARCH WITHOUT DANGER TO THE PUBLIC.

MAN: YOU MADE THE STATEMENT THERE'S NO KNOWN DANGEROUS ORGANISM HAS EVER BEEN PRODUCED BY A RECOMBINANT DNA EXPERIMENT.

YES.

NOW, JUST WHAT THE HELL DO YOU THINK YOU'RE GONNA DO IF YOU DO PRODUCE ONE?

THEY DON'T EVEN KNOW WHAT'S GONNA EVENTUALLY COME OUT OF THIS EXPERIMENTATION.

IT COULD BE ANYTHING.

IT COULD BE A CONTAMINATION...

INFECTIONS... SOMETHING THAT COULD CRAWL OUT OF THE LABORATORY SUCH AS A FRANKENSTEIN.

COBB: THIS WAS THE EARLY 1970s.

THERE WERE IMPORTANT POPULAR SCIENCE MOVEMENTS IN WHICH PEOPLE WERE INVOLVED IN TRYING TO UNDERSTAND WHAT SCIENCE WAS DOING.

MAN, ON VIDEO: THE PEOPLE ARE AT RISK AND AREN'T BENEFITING FROM THE EXPERIMENTS THAT ARE BEING DONE WITH RECOMBINANT DNA.

WHAT WE MIGHT WELL GET IS JUST A LOT OF MYSTERY DISEASES CROPPING UP IN A LOT OF DIFFERENT PLACES.

THE FUTURE OF THE SPECIES, THE TYPE OF CHILDREN WE WILL HAVE, THE TYPE OF CHILDREN WE WON'T HAVE, THE PEOPLE FEEL THAT THIS TYPE OF RESEARCH IS REALLY TAKING US DOWN THAT ROAD VERY QUICKLY.

NARRATOR: BUT THE GENIE WAS OUT OF THE BOTTLE, AS ENTREPRENEURS QUICKLY REALIZED THERE WAS LIMITLESS MONEY TO BE MADE USING THE NEW TECHNOLOGY.

ONE OF THEM WAS BOB SWANSON, A DOWN-ON-HIS-LUCK, 29-YEAR-OLD VENTURE CAPITALIST.

A CONNOISSEUR OF POPULAR SCIENCE MAGAZINES AND SCI-FI FILMS, HE HAD A HISTORY OF FAILED INVESTMENTS.

BUT WHEN HE HEARD ABOUT RECOMBINANT DNA, IN THE WINTER OF 1976, HE PLACED A CALL TO A PROMINENT EXPERT IN THE FIELD NAMED HERB BOYER.

SWANSON MET BOYER IN A CLUTTERED LAB AT THE UNIVERSITY OF CALIFORNIA AT SAN FRANCISCO AND LAID OUT A VISION FOR A NEW COMPANY WHOSE MISSION WOULD BE TO HARNESS RECOMBINANT DNA TO MAKE NEW DRUGS.

IT WOULD BE CALLED GENENTECH.

THEIR FIRST TARGET WOULD BE PARTICULARLY LUCRATIVE.

INSULIN--A LIFE-SAVING DRUG FOR MILLIONS OF PEOPLE WITH DIABETES.

IT WAS SO HARD TO MAKE INSULIN... BECAUSE YOU HAD TO EXTRACT IT FROM TENS OF THOUSANDS OF FETAL PIGS' PANCREAS JUST TO EXTRACT A FEW GRAMS OF INSULIN.

BUT WITH RECOMBINANT DNA, YOU HAVE NEW DRUGS THAT YOU COULD MAKE THAT YOU COULDN'T HAVE MADE 5 YEARS AGO JUST BY USING GENES.

NARRATOR: FRED SANGER, A BRITISH CHEMIST, HAD WORKED OUT THE AMINO ACID BUILDING BLOCKS OF THE INSULIN PROTEIN.

BOYER'S PLAN WAS TO CREATE THE EXACT DNA SEQUENCE THAT WOULD GIVE RISE TO THAT PROTEIN, ESSENTIALLY BUILDING AN ARTIFICIAL INSULIN GENE IN THE LAB.

THEN, USING RECOMBINATION, HE WOULD TRANSPLANT THIS CODE INTO BACTERIAL DNA AND WATCH AS THAT ORGANISM PRODUCED UNLIMITED QUANTITIES OF INSULIN PROTEIN.

THE PLAN WORKED PERFECTLY.

JORGENSEN: THE BEAUTY OF BIOTECH IS THAT YOU'RE TAKING SOMETHING AND JUST TWEAKING IT, HIJACKING IT, SO IT MAKES WHAT YOU WANT INSTEAD OF WHAT IT'S NATURALLY PROGRAMMED TO MAKE.

MUKHERJEE: THAT'S WHERE THE IDEA OF USING RECOMBINANT DNA, USING GENETIC ENGINEERING TO MAKE HUMAN MEDICINES BEGINS TO TAKE BIRTH IN AN ENTREPRENEURIAL SENSE, IN A REAL SENSE.

THAT'S WHERE IT'S BORN.

NARRATOR: INSULIN WAS JUST THE FIRST SUCCESS.

WITHIN A FEW YEARS, OTHER NEW DRUGS USING RECOMBINANT DNA WERE COMING ONLINE FOR DISEASES SUCH AS HEMOPHILIA, ANEMIA, AND GROWTH DISORDERS.

A NEW, MULTI-BILLION DOLLAR INDUSTRY WAS BORN.

THE SUCCESS OF BIOTECH FIRED THE IMAGINATION OF SCIENTISTS AND LAY PEOPLE ALIKE.

IF IT WAS POSSIBLE TO EDIT DNA TO CREATE MEDICINES, WHAT ELSE COULD BE DONE?

IT HERALDS A NEW MEDICAL TECHNOLOGY-- DRUGS BORN OF GENETIC ENGINEERING.

NARRATOR: CONTEMPLATING THE POSSIBILITY OF CURING DISEASE, RESEARCHERS AND THE PUBLIC WERE READY TO EMBRACE A NEW AGE OF GENETICS.

LUKE ROSEN HAS BEEN TRAVELING THE COUNTRY.

HE'S BEEN TRYING TO RAISE AWARENESS OF HIS DAUGHTER SUSANNAH'S RARE GENETIC ILLNESS AND HOPING TO FIND A WAY TO SLOW ITS PROGRESS.

WITHIN THE PAST YEAR, HE'S FOUND 50 MORE CHILDREN WITH THE DISEASE.

SO...THIS.

SO IF THIS IS WHAT YOU TYPICALLY SEE IN MAYBE A GENETICIST'S OFFICE, WELL, SO, THERE'S SUSANNAH, RIGHT-- CIRCLED.

P305L.

AND THESE ARE THE MUTATIONS THAT WE FOUND.

BUT IT'S WHEN THIS IMAGE BECOMES THAT IMAGE THAT MAYBE PEOPLE WILL WORK A LITTLE BIT FASTER.

NARRATOR: SPEED IS BECOMING MORE AND MORE ESSENTIAL, AS SUSANNAH GETS WORSE.

THE TENSION IS TAKING A TOLL ON LUKE AND HIS FAMILY.

GOOD.

ROSEN: THE THING THAT IS MOST TERRIFYING ABOUT KNOWING THAT SUSANNAH'S DISEASE IS PROGRESSIVE IS THE IDEA OF BEING PRESENT AND HOW CAN YOU BE PRESENT AND APPRECIATE EVERY SINGLE MOMENT, BUT AT THE SAME TIME ALMOST HAVE TO SCREAM FROM THE MOUNTAINTOP ABOUT THIS GENE?

SCIENTIFIC COMMUNITY, IS THERE ANY CHANCE YOU CAN WAKE UP AND GIVE US SOME ATTENTION HERE?

BUT THAT TAKES A LOT OF TIME AWAY FROM A LITTLE GIRL WHO'S GETTING WORSE.

NARRATOR: AT A CONFERENCE IN IRVINE, CALIFORNIA, LUKE AND HIS DAUGHTER'S DOCTOR, WENDY CHUNG, ARE HOPING TO FIND COMPANIES WORKING ON RARE DISEASES ALSO CAUSED BY A SINGLE GENE.

1, 2, 3.

PERHAPS ONE OF THEM HAS DEVELOPED A TREATMENT THAT MIGHT PROVIDE CLUES FOR TREATING SUSANNAH'S ILLNESS.

MAN: AND THOSE ARE THE GUIDELINES.

AND IF YOU HAVE ENOUGH DATA, YOU CAN MAKE PREDICTIONS ABOUT A PATIENT THAT... CHUNG: THIS IS AN UMBRELLA MEETING FOR RARE DISEASES.

SO, FOR THE THOUSANDS OF RARE DISEASES, BEING ABLE TO HAVE PATIENTS, FAMILIES, RESEARCHERS COME TOGETHER AND REALIZE THAT ALTHOUGH INDIVIDUALLY THE CONDITIONS MIGHT BE RARE, COLLECTIVELY THEY'RE QUITE COMMON, AND THERE ARE A LOT OF THINGS THAT WE CAN LEARN FROM EACH OTHER.

[CAMERA SHUTTERS CLICKING] THANK YOU.

MAN: WHAT BRINGS YOU OUT TO THIS WONDERFUL EVENT THIS EVENING?

ROSEN: MY DAUGHTER, REALLY, IS WHO BRINGS ME HERE--SUSANNAH.

SUSANNAH'S AT HOME.

SHE'S 4.

AND SHE HAS A RARE GENETIC DISEASE AND TWO YEARS AGO, WE STARTED A FOUNDATION TO... NARRATOR: THERE IS SOME EXCITING NEWS AT THE CONFERENCE.

A NEW COMPOUND IS BEING TESTED IN ANOTHER NEUROLOGICAL DISEASE, HUNTINGTON'S, THAT IS SHOWING PROMISING RESULTS.

YEAH.

SO ONE OF THE THINGS I THOUGHT WAS EXCITING IS SEEING WHAT THEY'RE DOING WITH THE OLIGONUCLEOTIDE TREATMENT.

IN TERMS OF HUNTINGTON'S.

AND I HAVE TO SAY, I WAS IMPRESSED IN TERMS OF HOW FAR THEY'VE GOTTEN.

THE SAFETY DATA LOOKED GOOD.

TO ME, IT LOOKS MORE PROMISING THAN I'VE SEEN IT BEFORE.

ANYTHING WITH HUNTINGTON'S, ALS, ALZHEIMER'S--THAT KIND OF PERKED MY EARS.

YEAH, SPECIFICALLY THE HUNTINGTON'S.

JUST--AS YOU'RE HEARING ABOUT IT, AND IF YOU'RE SEEING THAT SOMETHING'S WORKING FOR HUNTINGTON'S, DEFINITELY JUST LISTEN A LITTLE BIT MORE CAREFULLY IN SEEING IF SOMETHING'S GONNA WORK FOR THAT.

YEAH, YEAH.

IT'S POSSIBLE THAT SAME STRATEGY'S GONNA WORK FOR US.

OK.

I'LL TRACK THEM DOWN.

SO... NARRATOR: THE NEW HUNTINGTON'S DRUG THAT IS CAUSING SO MUCH EXCITEMENT AT THE CONFERENCE IS BEING TESTED ON PATIENTS IN A CLINICAL TRIAL IN LONDON.

SO THIS IS A VIAL OF THE DRUG.

SO THIS VIAL CONTAINS A SINGLE DOSE OF THE DRUG THAT WE'VE BEEN INJECTING INTO THE SPINAL FLUID OF OUR PATIENTS.

MILLIONS OF DESIGNER DNA MOLECULES FLOATING AROUND IN A SOLUTION.

AND THOSE ARE INTENDED TO REDUCE PRODUCTION OF THE PROTEIN THAT CAUSES HUNTINGTON'S DISEASE.

THE IDEA THAT A PROBLEM AS BIG AS HUNTINGTON'S DISEASE COULD HAVE A SOLUTION SO SMALL THAT YOU CAN HOLD IT BETWEEN TWO FINGERS IS QUITE OVERWHELMING, TO BE HONEST.

SMALL VIAL OF HOPE.

[ALL TALKING INDISTINCTLY] NARRATOR: PETE ALLEN, ONE OF 3 SIBLINGS WITH HUNTINGTON'S IN THE UK, HAS BEEN ON THE NEW DRUG FOR ABOUT A YEAR.

ALLEN HAD FOUND OUT IN 2006 THAT HE WAS AT RISK FOR HUNTINGTON'S WHEN HIS OLDER SISTER TOLD HIM THAT SHE HAD TESTED POSITIVE FOR THE DISEASE AFTER NOTICING SIGNS OF IT IN THEIR MOTHER.

WOMAN: WE WERE JUST LIVING IN OUR HAPPY BUBBLE, AND THEN THAT BUBBLE BURST REALLY SUDDENLY.

IN ONE SENTENCE, SHE CHANGED ALL OUR FUTURES.

HEY, PETER.

HOW ARE YOU?

NARRATOR: STILL NOT KNOWING AT THE TIME WHETHER HE, TOO, HAD THE GENE... HAVE A SEAT.

PETE DECIDED TO TAKE THE HUNTINGTON'S TEST.

FOLLOW THE TIP OF MY FINGER, SIDE TO SIDE.

WOMAN: YOUR MAIN MOTIVATION FOR HAVING THE TEST WAS-- IT WAS TOO LATE.

WE'D ALREADY HAD 3 CHILDREN.

AND WHAT YOU WANTED TO DO WAS GET INVOLVED IN AS MUCH RESEARCH AS YOU COULD TO TRY TO WORK TOWARDS A CURE FOR FUTURE GENERATIONS.

THAT WAS YOUR BIG MOTIVATOR FOR HAVING-- I CAN'T REMEMBER THAT AT ALL.

I THINK THAT'S A BIT POST- RATIONALIZATION I THINK, PRIMARILY, I WANTED TO HAVE THE TEST TO...

CARRY ON WITHOUT IT IMPACTING ON ME.

IT'S THE ONE THAT YOU HATE.

PETER: I'M AN OPTIMIST AS OPPOSED TO A...

NEGATIVE PERSON.

ANNIE: YOU ARE.

YOU ARE AN OPTIMIST.

AND I THINK THAT'S STOOD YOU IN GOOD STEAD, HASN'T IT?

STAY.

NARRATOR: IN 2016, PETE BECAME ONE OF THE FIRST PATIENTS TO ENROLL IN THE CLINICAL TRIAL OF THE NEW HUNTINGTON'S DRUG.

HE'S ONE OF FEWER THAN 50 PEOPLE IN THE WORLD RECEIVING THE TREATMENT.

SO THE MOMENT WHEN I'M ON THE TARGET, IT'S JUST EUPHORIC AND-- IT'S A DIFFICULT WORD FOR ME TO SAY WITH MY MOUTH.

HA HA!

EUPHORIC.

JUMPING UP AND DOWN.

ANNIE: YEAH, 'CAUSE YOU'VE BEEN GIVEN SOME HOPE, AND THERE ARE SO MANY FAMILIES DESPERATE TO GET THEIR LOVED ONES ONTO A TRIAL.

GOOD.

ALL RIGHT.

I'LL STOP YOU THERE.

THAT'S BEST I HAVE DONE.

THAT WAS REALLY GOOD.

ANNIE: SO YOU FEEL LIKE, YOU KNOW, YOU'RE INCREDIBLY LUCKY.

IT'S LIKE IN "CHARLIE AND THE CHOCOLATE FACTORY," AND YOU'VE BEEN-- YOU'VE GOT ONE OF THE GOLDEN TICKETS.

[SPEAKING INDISTINCTLY] NARRATOR: IT'S BEEN 4 WEEKS SINCE PETE'S NIECE JENNY TOOK THE HUNTINGTON'S TEST.

SHE'S NOW GOING IN FOR HER RESULTS.

YOU OK?

NO?

JENNY: YOU KNOW, I KNOW THAT THERE'S NO ACTUAL CURE YET, BUT ALL OF THE TRIAL AND EVERYTHING THAT'S HAPPENING WITH IT HAS JUST MADE IT, FOR ME, LESS OF A SCARY THING TO FIND OUT, AND ALSO...MADE ME WANT TO KNOW SO THAT WHATEVER TRIALS THERE ARE IN THE FUTURE I CAN TAKE PART IN THEM.

WOMAN: OK, WELL, TAKE A SEAT BOTH OF YOU.

[CHAIRS SCRAPE ON FLOOR] OK, SO I'M GONNA GO STRAIGHT TO IT.

I'VE GOT GOOD NEWS, JENNY.

OK, YOUR RESULT IS NORMAL, SHOWING THAT YOU HAVE NOT INHERITED HUNTINGTON'S DISEASE.

[SNIFFS, CRYING] OH...

IT'S OK. OK. OH... HOW ARE YOU FEELING?

I DON'T EVEN KNOW.

IT FELT LIKE...

I JUST... LIKE EVERYTHING EXPLODED FOR ME ALL SUDDENLY.

I THINK EVERYTHING I THOUGHT ABOUT... EVERYTHING... YEAH.

OOH, LOT OF PRESSURE RELIEVED.

YEAH.

TAKE ALL THE TIME THAT YOU NEED.

I JUST LITERALLY NEVER EVEN IMAGINED LIKE HEARING THAT RESULT.

NOW I'VE GOT TO WATCH IT 7 MORE TIMES.

WOMAN: YEAH, SO MIXED FEELINGS, OF COURSE, AND WE TOUCHED ON THAT IN THE PREVIOUS SESSION, DIDN'T WE, ABOUT HOW EVEN A GOOD NEWS RESULT FOR YOU BRINGS UP A NUMBER OF FEELINGS.

THEY'VE ALWAYS SAID, LIKE, THEY'RE PROUD AND THAT IT'S BRAVE TO BE THE FIRST ONE TO DO IT, AND ONE OF US ALWAYS HAD TO.

AND, YOU KNOW, MY COUSIN MESSAGED ME AND SAID, LIKE, "LET'S HOPE IT'S ONE OF THE FIRST OF A LONG LINE OF NEGATIVE RESULTS."

LIKE, YOU KNOW... AND I KNOW THAT IT'S A START OF A LOT OF PEOPLE THAT HAVE TO GO THROUGH IT.

I DON'T HAVE IT.

OH.

[CRYING] [KISSING] [KISSING] OHH!

[CRYING] I THINK IT WAS SLOWING YOU DOWN.

[LAUGHTER] I CAN'T EXPLAIN.

I JUST... YOU'RE ALL UPSET.

[LAUGHTER] OH!

OH.

WOW.

NARRATOR: THE NEWS IS ALSO ENCOURAGING FOR JENNY'S UNCLE PETE.

6 MONTHS INTO THE TRIAL, HE HAS NOTICED REAL IMPROVEMENTS.

SO I CAN WRITE NOW, SIGN MY NAME.

ANNIE: HE WAS REALLY STRUGGLING TO SIGN HIS NAME, AND YOU DON'T REALIZE HOW OFTEN YOU HAVE TO SIGN DOCUMENTS IN LIFE.

I HAVEN'T SEEN PETE WRITE LIKE THIS FOR...

I DON'T KNOW.

I MEAN, YOU'D STOPPED EVEN TRYING.

YEAH.

SO THAT'S FANTASTIC TO SEE IMPROVEMENTS.

WELL DONE!

THANK YOU.

[CHUCKLING] NARRATOR: SCIENTISTS HAVE SEEN MAJOR REDUCTIONS IN THE MUTANT PROTEIN THAT CAUSES HUNTINGTON'S IN PATIENTS ON THE TRIAL.

THE COMPOUND WILL NOW BE TESTED IN SEVERAL HUNDRED PATIENTS WORLDWIDE TO ANALYZE WHETHER IT REALLY CAN SLOW DOWN THE DISEASE.

HERE?

NARRATOR: THE COMPANY THAT DEVELOPED THE HUNTINGTON'S DRUG THAT IS HELPING PETE ALLEN... ARE YOU GONNA PLAY THE PIANO FOR US?

IS NOW WORKING ON A SIMILAR COMPOUND FOR KIF1A, THE DISEASE AFFLICTING SUSANNAH ROSEN.

SUSANNAH: BECAUSE I'M PLAYING A LESSON.

CHUNG: OR ARE YOU TAKING A LESSON?

NARRATOR: THE NEXT STEP WILL BE TO INJECT IT INTO THE MOUSE MODEL THAT THE ROSENS FOUGHT SO HARD FOR TO SEE IF IT ALLEVIATES THE ANIMAL'S SYMPTOMS.

♪ ...TWINKLE, LITTLE STAR... ♪ BEFORE LONG, IT IS HOPED, IT CAN BE TRIED ON CHILDREN LIKE SUSANNAH.

♪ ...WHAT YOU ARE ♪ ROSEN: YAY!

I'M NOT FINISHED!

[CHUCKLING] OH, I'M SO SORRY!

WHAT I WANT THE MOST IS FOR SUSANNAH NOT TO BE IN PAIN AND FOR SUSANNAH TO NEVER KNOW WHAT THE WORD "DEGENERATIVE" MEANS.

I WANT HER TO BE HAPPY AND LAUGHING AND FEEL LIKE SHE IS A...

THE WONDERFUL, AMAZING LITTLE GIRL THAT SHE IS.

[VOICE CRACKING] I WANT HER TO KNOW THAT.

TSK.

ALL RIGHT, YOU GOT THIS.

I GOT THIS.

YOU GOT THIS.

BOTH, SINGING: ♪ 1, 2, EVERYWHERE I GO ♪ ROSEN: SHE WORKS SO DAMN HARD EVERY DAY, AND IT'S OUR RESPONSIBILITY TO GIVE HER THE OPPORTUNITY TO KEEP WORKING THAT HARD.

IF WE STOP DOING WHAT WE'RE DOING AND WE STOP FIGHTING FOR A TREATMENT AND WE STOP FUNDRAISING, WE STOP DOING ALL THIS, THEN WE'RE NOT HOLDING UP OUR END OF THE BARGAIN, BECAUSE THAT LITTLE GIRL WORKS HARDER THAN ANYBODY.

I'M RIGHT HERE IF YOU NEED A...

BUT STILL, WE HAVE THIS TREMENDOUS SENSE OF HOPE THAT WE WILL DISCOVER A WAY TO FIND TREATMENT FOR THESE KIDS.

AND EVERY FAMILY WITH A GENETIC DISEASE DESERVES TO HAVE THAT HOPE.

WALK ON.

WALK ON.

CHUNG: THE EXCITEMENT FOR ME IS THAT FOR THE FIRST TIME THERE IS TREMENDOUS OPPORTUNITY FOR A LOT OF PEOPLE WHO HAVE BEEN LIVING THEIR LIVES, AND EVEN GENERATIONS WITHIN FAMILIES, THAT CAN NOW SAY, "I CAN SEE THAT LIGHT AT THE END OF THE TUNNEL."

AND THAT TUNNEL IS NOT SO FAR AWAY.

THAT TUNNEL IS SOMETHING THAT WE CAN ALL FEEL, I THINK, WITHIN OUR LIFETIME.

HO HO HO!

ROSEN: HEY.

I LOVE YOU.

ANNOUNCER: NEXT TIME ON "THE GENE"... MAN: IT'S THE UNIVERSAL CODE OF LIFE ITSELF.

ANNOUNCER: FROM MYSTERY TO GENE MAPPING... MAN: AND WITH GENE EDITING, WE CAN MAKE THE FIX ONCE... ANNOUNCER: THE BREAKTHROUGHS... MAN: AND THE PATIENT WILL BE PERMANENTLY CURED.

ANNOUNCER: THE HURDLES... MAN: CANCER IS A DISEASE OF THE GENOME.

MAN: IT'S THOUSANDS OF DISEASES.

NARRATOR: THE HEARTBREAKS.

MAN: WE'RE DESPERATE.

WE'RE DOING EVERYTHING THAT WE CAN DO TO KEEP HER ALIVE.

ANNOUNCER: NEXT TIME ON "THE GENE: AN INTIMATE HISTORY."

TO KEEP HER ALIVE.

♪ ANNOUNCER: WATCH THE FULL FILM AND FIND ADDITIONAL INFORMATION AT PBS.ORG/THEGENE JOIN THE CONVERSATION WITH #THEGENEPBS TO ORDER "THE GENE: AN INTIMATE HISTORY," ON DVD, VISIT SHOPPBS.ORG.

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♪