TALITHIA WILLIAMS: What do you wonder about?

MAN: The unknown.

What our place in the universe is.

Artificial intelligence.

Hello.

Look at this, what's this?

Animals.

An egg.

Your brain.

RANA EL KALIOUBY: Life on a faraway planet.

WILLIAMS: "NOVA Wonders"-- investigating the biggest mysteries.

We have no idea what's going on there.

These planets in the middle we think are in the habitable zone.

WILLIAMS: And making incredible discoveries.

WOMAN: Trying to understand their behavior, their life, everything that goes on here.

MAN: Building an artificial intelligence is going to be the crowning achievement of humanity.

WILLIAMS: We're three scientists exploring the frontiers of human knowledge.

ANDRÉ FENTON: I'm a neuroscientist and I study the biology of memory.

EL KALIOUBY: I'm a computer scientist and I build technology that can read human emotions.

WILLIAMS: And I'm a mathematician, using big data to understand our modern world.

And we're tacking the biggest questions...

Dark energy?

ALL: Dark energy?

WILLIAMS: Of life... DAVID PRIDE: There's all of these microbes, and we just don't know what they are.

WILLIAMS: And the cosmos.

♪ ♪ WILLIAMS: On this episode, DNA is really just a chemical.

WILLIAMS: We're rewriting the code of life like never before.

DREW ENDY: There's enough DNA to make 30 copies of every human genome on the planet.

GEORGE CHURCH: You can change every species to almost anything you want.

WILLIAMS: Can this new genetic power save lives?

Or even bring extinct creatures back from the dead?

BETH SHAPIRO: Could we bring a mammoth back to life?

(roaring) WILLIAMS: It's a revolution in biology.

WOMAN: This is rapid man-made evolution.

WILLIAMS: "NOVA Wonders"-- "Can We Make Life?"

(babies crying) Major funding for "NOVA Wonders" is provided by... WILLIAMS: The earth is brimming with an unimaginable variety of life, a multitude of creatures connected and intertwined in countless ways.

They've evolved over a billion years driven by a very simple code.

EL KALIOUBY: For decades, scientists have been trying to master this chemical cipher that we call DNA.

WILLIAMS: Now, suddenly, new tools are allowing researchers to manipulate the code of life with incredible precision.

How powerful is this?

Could we change and mold life at our command?

Could we bring extinct creatures back from the dead?

(woolly mammoth growling, roaring) How much power do we really have over life?

(giggles) And are we ready to use it wisely?

I'm André Fenton.

I'm Rana el Kaliouby.

I'm Talithia Williams.

And in this episode, "NOVA Wonders"-- (tiger growls) "Can We Make Life?"

♪ ♪ (crying) 15,000 years ago, the biggest thing on four legs was this guy-- the mammoth.

(mammoth growling) These eight-ton giants threw their weight around, from the steppes of Europe to the plains of North America, until they vanished from the face of the earth.

SHAPIRO: From the paleontological record, the best guess is that there were many mammoths, potentially hundreds of thousands, even to millions of mammoths.

WILLIAMS: Evolutionary biologist Beth Shapiro deciphers the DNA-- the genetic code-- of ancient animals, like the Ice Age mammoths discovered here in Hot Springs, South Dakota.

It's a absolutely unique site, really amazing.

This is a ancient sinkhole where lots of mammoths would have wandered up into a lake to have a drink and once got stuck, not been able to get out.

There are about 60 mammoths that are in this site in a pretty tightly condensed little geographic area.

WILLIAMS: These animals died at least 26,000 years ago, before people came to North America.

When human hunters did show up, mammoths wouldn't stand a chance.

SHAPIRO: People might have been that proverbial straw that breaks the camel's back.

These animals were in trouble because the climate was changing, because there wasn't enough habitat available to them, just not enough to eat.

And then just at that really worst moment, people turned up.

WILLIAMS: Pretty soon, all the mammoths, including the iconic woolly mammoth that loved colder climates, would go extinct, gone forever.

Or are they?

♪ ♪ If George Church has his way, he will bring the woolly mammoth back from the dead to roam the earth once again.

Kind of tall and woolly like a mammoth himself, George is one of the world's most inventive genetic scientists.

He once coded his latest book in DNA and brought it on this piece of paper to the Stephen Colbert show.

They took the book, including the photographs...

Yes?

Zeroes and ones-- converted to A, C, Gs and Ts.

Which is the code of DNA, Put a little drop that contains some DNA in there.

That's right.

So this piece of paper right there contains 20 million copies of this book.

That's right.

(laughter) Well, Dr. George Church... WILLIAMS: But can this genetic magician possibly resurrect a long-dead woolly mammoth?

CHURCH: Every species on the planet comes from a cell with a genome, and that means you can change it to almost anything you want.

WILLIAMS: George is like the fictional scientists from "Jurassic Park."

They "de-extincted" dinosaurs by implanting their DNA into ostrich eggs.

Come on, little one, come on... WILLIAMS: The baby dinosaurs that hatched were cute at first, and then they weren't.

(roaring) Despite the movie's dubious science, George's de-extinction idea is not very different, And, fortunately, his creatures are vegetarians.

George's real life plan is to take mammoth genes decoded from ancient remains and implant them into the embryo of a live Asian elephant.

CHURCH: They're very closely related to the mammoths.

Even though they don't look that way, they're genetically very similar.

WILLIAMS: And then he hopes the Asian elephant's new baby will come out woolier and more mammoth-like than this one.

At least, that's the plan.

Why would anyone think they could reverse evolution and bring an extinct creature back to life?

(mammoth growls) The answer lies deep inside almost every living cell in your body-- in your DNA.

One of the wonders of DNA is how simple it is-- a double string made of four chemicals usually known by their initials: A, T, C, and G. Strings of these letters form genes, the coded instructions that tell a cell to build specific proteins.

Arrange the letters one way, and you'll get keratin.

It's not just a hair treatment.

It's the main protein making up our hair, skin, and fingernails.

Switch the order of the letters, and you could get ricin, a protein made in the seeds of a castor oil plant, and to a human, extremely poisonous.

DNA and the order of its letters are the instructions that turn a fertilized egg into a flounder, a frog, or a fly.

The quest to use DNA to control and manipulate life began over 40 years ago on creatures a whole lot smaller than elephants in an attempt to treat a deadly disease.

In the 1970s, Herb Boyer and Stanley Cohen began using new DNA technology to see if they could coax common E. coli bacteria into producing human insulin protein.

People with diabetes don't produce enough insulin to help their bodies absorb sugar and other nutrients and will die without injecting it.

Before the 1970s, insulin was extracted from cattle and pigs.

Unfortunately, insulin from these animal sources sometimes caused severe allergic reactions.

But the Boyer team was about to change that.

Their idea was to engineer E. coli bacteria by first cutting its genetic material with enzymes and then inserting a synthetic version of the human insulin-coding gene into the gap.

Amazingly, the altered bacteria not only copied the human gene whenever it divided, they produced human insulin-- a lifesaver for diabetics ever since.

ARTHUR CAPLAN: I found it amazing as a non-biologist that you could trick a tiny microbe into making something that it doesn't naturally make and reorient it to make something that we want.

WILLIAMS: Here in a biochemical lab at M.I.T.... We actually should go back and reduce... WILLIAMS: Kristala Jones-Prather leads a team that is also altering the genes of microbes to make proteins and chemicals that are useful to us.

KRISTALA JONES-PRATHER: You can actually look at those individual cells as little factories.

If you shrunk yourself down to the size of a molecule, you would just see lots and lots of chemical reactions.

WILLIAMS: But you need trillions of organisms to produce enough of these tiny chemicals to be useful commercially.

So today, biotech companies use giant fermenters filled with microorganisms to pump out a slew of bio products, all thanks to our ability to manipulate DNA.

JONES-PRATHER: The key observation that really fueled the entire biotech industry was recognizing that DNA is really just a chemical.

And the structure is what matters, and so it doesn't matter if that DNA came from a horse or a mouse or something you dug off the bottom of your shoe, the DNA is still just the DNA.

WILLIAMS: Today, production facilities not only make bio-products, they make synthetic DNA and can even process the four basic chemicals into an exact genetic sequence you can order online.

You'd go to a website for a company, a DNA synthesis company, and you'd submit to that website this... the sequence of DNA you want.

NILLI OSTROV: We can take the entire gene sequence and copy, and then put it in an order sheet.

You can say T-A-A-T-A-C-G-A C-T-C-A-C-T-A-T A-G-G-G-A-G-A.

Give them a credit card number.

Order this DNA.

They'll print that DNA and put it in an envelope and mail it to you.

OSTROV: We get the gene back in a tube in about a day or two.

It's DNA that is made from scratch by the machine.

This is a bottle is full of the letter A.

Not the letter in the alphabet, but the base of DNA.

There's ten grams of stuff in here, and it costs about $250 for the bottle.

This is enough material to make approximately 30 copies of every human genome on the planet.

EL KALIOUBY: So think about what this means.

All the convenience of online shopping.

Just like I can custom order a car.

Do I want the silver?

Or the red?

Or build my own pizza.

Extra cheese... Mushrooms.

Definitely not anchovies.

Perfect.

Along with all the stuff you can buy online, amazingly, you can custom order actual DNA.

So now, with a credit card and a computer, not only can you build your own jeans, you can build your own genes.

WILLIAMS: Our ability to build and manipulate the genes that control life means we now have the power to remake life.

And this young scientist is trying to prove it with one of the most daring genetic experiments on the planet.

Kevin Esvelt wants to stop a growing menace on Nantucket and Martha's Vineyard, beautiful island communities off the coast of Massachusetts.

(gulls crying) On the surface, you wouldn't notice anything especially scary on Nantucket.

Tourists flock here, and others live year-round to enjoy the beauty, fun, and comforts of island life.

What they don't come for, but often get anyway, is Lyme disease.

Devin, why don't you come on down.

WILLIAMS: Dr. Timothy Lepore is a 30-year veteran of treating Lyme disease on Nantucket.

In the spring and summer on Nantucket, if I see somebody like that, that's Lyme disease.

WILLIAMS: Lyme is a bacterial infection that often starts with a rash where a person has been bitten by an infected tick.

You get rashes... WILLIAMS: Most people can be cured with antibiotics that eliminate the rash, fever, and joint pain within a few days.

LEPORE: When we treated you, you got better.

Yep.

And then the next day, it had the ring around it.

WILLIAMS: But not everyone recovers so quickly.

LEPORE: People that have had long-standing Lyme disease may have some persistent issues.

If you wait, you can have delayed symptoms like complete heart block, where your heart starts beating 20 to 30 times a minute, or you can have a facial palsy where it looks like one side of your face is paralyzed.

Come on in.

KEVIN ESVELT: Lyme is the single most common infectious vector-borne disease in the United States.

It's way more common than Zika.

It's way more common than West Nile, anything like that.

The areas of Nantucket and Martha's Vineyard are number two and number three when it comes to incidence of tick-borne disease in the United States.

WILLIAMS: Kevin Esvelt is on a mission to eradicate Lyme disease.

And for him, these Massachusetts islands are the perfect places to start.

This pocket of dense vegetation is typical of Nantucket and the rest of the Northeast.

Try to find an easy way out.

WILLIAMS: Sam Telford is working with Kevin.

An expert on ticks and tick-borne diseases, Sam's diving into this brush because he knows it's literally crawling with ticks for him to study.

Dragging a white furry cloth, Sam is hoping to catch ticks that think the cloth is an animal.

SAM TELFORD: Ticks are what we call ambush predators.

They sit there on a blade of grass and they've got their front legs sticking out, and then as you walk by, they'll latch on to something they think is furry.

There is one here.

WILLIAMS: This is a tick in an early stage, when it's very tiny.

No one who gets Lyme disease recalls that they were bitten by a tick simply because of their small size.

How on earth are you going to see something that small?

WILLIAMS: Humans get Lyme disease from ticks.

But ticks are not born with Lyme bacteria.

They get it by feeding on this innocent-looking critter-- the white-footed mouse that carries Lyme bacteria in its blood.

And another innocent-looking creature, the deer, is a crucial link in the chain of transmission to us.

Baby ticks will often feed on mice that are close to the ground.

This is when they get the Lyme bacteria.

As the ticks grow, they will feed on other mice, deer, or people, passing the Lyme bacteria with each bite.

But only people get the disease.

A single deer is like an all-you-can-eat buffet.

They live in the woods and can't easily scratch ticks off.

So female ticks become engorged, drop off, lay eggs, and the cycle starts again.

ESVELT: The typical deer has several thousand ticks attached to it.

And the females will each lay several thousand eggs.

So when you see a deer wandering around through the woods, you can think, "That is the walking equivalent of a million ticks in the next generation."

WILLIAMS: But people adore seeing deer and don't want them removed.

Could it be childhood memories of Bambi?

ESVELT: It is Bambi.

(laughs) We like seeing deer.

So, because there are so many more deer than there have ever been before, historically, there are many more ticks than there have ever been before.

WILLIAMS: Now, deer shed ticks in our lawn clippings, garden plots, recreation areas, and if they carry the Lyme bacteria, they can give it to us.

Here on Nantucket, 40% of residents have caught Lyme disease.

And it's not the only tick-borne disease they have to worry about.

TELFORD: There's an infection called Nantucket fever or human babesiosis, which was first identified here in 1969.

It's a malaria-like infection and it actually kills people.

WILLIAMS: There are four serious tick-carried diseases on the island, with Lyme by far the most common.

But it's not just these tiny islands.

Mice, deer, and ticks have spread Lyme disease throughout the northeast U.S.

Almost anyone in the region who ventures outdoors-- not just into the woods, but in suburbs, too-- is putting themselves at risk.

(exclaims) WILLIAMS: For Kevin Esvelt, it's a risk people should not have to take, especially with their kids.

ESVELT: I'm from the west coast, and there we have ticks, but they're so rare that I spent my childhood running around through the woods and never once got bitten by a tick, not once.

Come on, down the slide.

Whoa!

ESVELT: I have two kids.

It's just terrible that we have to be wary of them just running in the woods.

So, the notion that you can wander out here through some of the worst areas, and end up with lots of ticks on you is just... well, it's frankly horrifying.

All right, so I have 40 traps out in this site.

WILLIAMS: Kevin has a plan to make the outdoors safe again.

The mice seem to be wary today.

WILLIAMS: He believes he can get rid of Lyme disease by genetically altering the white-footed mice that carry it.

And if that goes well, he hopes to edit their DNA so they could resist ticks entirely.

Oh, looks like we've got one to take back.

ESVELT: Enlisting mice in the war against tick-borne disease would just be an amazing proposition.

I'm counting 18 on the ears.

WILLIAMS: The number of ticks is astounding, especially on its ears.

And if this mouse has the Lyme bacteria, all the ticks will become infected and can transmit the disease to us.

Kevin's plan is to make the mice resistant to Lyme bacteria with the help of genetic engineering's most exciting and powerful tool-- CRISPR.

CRISPR stands for clustered regularly interspaced short palindromic repeats.

(crowd groans) That's why it's just called "CRISPR."

First discovered in bacteria, CRISPRs are like bacterial immune systems.

They have two key parts-- a destroyer protein, like one called Cas9, and a piece of RNA that matches viruses that previously infected the bacteria.

If the same virus were to invade again, the RNA would recognize the invader's DNA, attach itself to its old enemy, and its Cas partner would slice the virus's DNA, destroying it.

A few years ago, some researchers realized they could use CRISPR to edit the genome of any living organism.

Here's the idea.

Say I have a stretch of DNA, maybe a part of a gene I'd like to change.

If I know the sequence of letters there, I can build a CRISPR that carries a matching code.

Once inside the cell, CRISPR will scan the DNA until it finds that exact spot.

And when it does, it slices the DNA right there.

Now I have a broken gene, but it turns out I can insert a new sequence into the gap, and that makes CRISPR potentially an extremely powerful tool.

CRISPR Cas engineering is much faster, it's much less expensive, and it's much easier to make those changes you want to make.

The really significant revolution with CRIPSR Cas9 is that, as far as I can tell, it pretty much works in any organism that you try it in.

WILLIAMS: And M.I.T.

's Kevin Esvelt wants to use CRISPR to change the DNA of mice and make them immune to Lyme bacteria.

ESVELT: The original idea that sparked this whole process was very simple.

Hey.

Hi.

Animals like us, and also mice, when we get sick with something, our immune systems evolve an antibody, often lots and lots of antibodies, that are really, really good at telling the immune system "This is the enemy, kill it."

WILLIAMS: But these antibodies do not get passed on to our children.

So we need vaccines to give us antibodies against certain diseases.

But there is no human Lyme vaccine.

And even if there was one for mice, he couldn't just line them up for shots.

So instead, Kevin wants to give them a genetic vaccine.

Here's how that would work.

First, Kevin, with the help of Sam Telford, infects mice in the lab with Lyme bacteria.

These mice quickly develop robust, Lyme-resistant antibodies.

Next, the team deciphers the genetic code that can create those antibodies.

They make this antibody gene in the lab.

And inject it, along with CRISPR genes, into the developing sperm cells of Sam's lab mice.

There, CRISPR would clear the way for the new gene to slide into the mouse's genome.

Now, if an engineered male mates with a wild female, roughly 50% of their babies, boys and girls, will inherit the Lyme-resistant gene and begin spreading it to future generations of mice.

That is, if Kevin's plan works.

(ship horn sounds) But before he can even try, he'll need Nantucket residents to approve the release of genetically modified mice, something many people here worry might backfire like the disastrous cane toad experiment.

♪ ♪ Cane toads were introduced to Australia in the 1930s to help kill off sugar cane beetles.

But instead, they became a biological wrecking ball.

A foreign species with no natural predators, they quickly overran the country.

Poisonous to animals, they've killed countless pets and native species, disrupted key parts of the country's ecosystem, and they are now almost impossible to get rid of.

The mice used in Kevin's experiment will be native, not foreign.

But some people worry that genetically modifying animals could spell trouble.

LEPORE: If you fool with Mother Nature, very often it doesn't turn out well.

So are we going to have mice the size of boxer dogs, I don't know.

WILLIAMS: As Kevin releases a wild mouse caught earlier, he hopes that someday the little creature jumping away will be resistant to Lyme disease.

But to get that far, he will need the island's complete trust.

And the jury is still out.

♪ ♪ Will people's fear of genetic engineering prevent Kevin from using this controversial science?

ELEONORE PAUWELS: You know, this is a technology too powerful for humankind to refuse.

It's going to help us transform not only our bodies and our genes, but can give us a chance to actually play a role in our own evolution.

WILLIAMS: George Church is certainly playing with evolution by attempting to de-extinct a woolly mammoth.

(growling, trumpeting) But why does this gene giant even want to do this?

George is one of those people in science who is just larger than life.

He just wants to be doing those most exciting projects at the cutting edge of whatever it is.

Wow, that is the coolest dry ice I have ever seen.

WILLIAMS: George's lab is renowned for stretching the limits of genetic engineering, from experiments using pigs to grow human organs for transplantation, to using bacterial DNA to encode and store data and even digitize movies.

But the woolly mammoth would be his greatest accomplishment yet.

Seeing a real mammoth again would be amazing.

Or what about sabre tooth tigers, or giant dodo birds, even flocks of passenger pigeons?

Bringing back extinct creatures wouldn't just be cool, we could see how these magnificent animals once lived and maybe find out how to save today's creatures from going extinct.

Which is exactly what George Church wants to do for the Asian elephant.

♪ ♪ WILLIAMS: George's plan is to combine the genes of a woolly mammoth with those of Asian elephants because making them mammoth-like might save them.

Hunted for their tusks and chased from farmlands, Asian elephant numbers are shrinking.

But George has a possible solution.

If you gave them access to one of the largest ecosystems on the planet, which is the arctic tundra where their very close relatives used to roam, that would probably save the species.

WILLIAMS: There's plenty of open, fertile space in the tundra, but it's too cold for warm-weather elephants to survive here.

So George's resurrection plan begins with genetically winterizing Asian elephants to become more like woolly mammoths, who loved the cold.

The team first identifies the specific genes in modern animals that code for things like fat or thick hair.

Then they look for their genetic counterparts in decoded mammoth genomes.

Once they identify the mammoth's "cold" genes, they make them synthetically, and insert them into living cells taken from an Asian elephant to see if they work.

BOBBY DHADWAR: What we're seeing here is green cells-- these are elephant cells that we've introduced mammoth DNA into.

The brighter the green that we're seeing means the more DNA has taken up.

WILLIAMS: In the lab, they've edited about 35 functioning woolly mammoth genes into the Asian elephant genome.

This is a good start for making a semi woolly mammoth.

But it's the next step that will be the most challenging.

SHAPIRO: There is a huge difference obviously between a cell growing in a dish in a lab and a baby mammoth wandering around.

How do I take that cell and turn that into an actual living, breathing organism?

(elephant trumpets) WILLIAMS: They could try and fertilize the egg cell of a captive Asian elephant with woolly mammoth genes.

But this is difficult.

SHAPIRO: It's very hard for them to get pregnant in captivity.

The pregnancies often don't go to term.

And this is probably has to do with the psychology of being in captivity.

WILLIAMS: And performing such an operation on an endangered species like this may simply be too great a risk.

♪ ♪ So George is studying mammals like the platypus and spiny anteater, whose babies develop outside a mother's body in an egg.

SHAPIRO: Could he possibly engineer a living mammoth this way?

(cracking) Can you imagine a baby woolly mammoth hatching out of an egg?

Really?

Not even George has figured out how to do this.

And what would this sort of mammoth be like?

(trumpets) CAPLAN: I think you're going to get a creature that's sort of a pseudo mammoth, not quite the same makeup.

So I think you're going to get a sort of echo of the animal that once was but not a replica.

So even if we could get to the point where we could transform this elephant to a living, breathing baby mammoth, a question that I have really is should we?

We know that elephants are very social creatures.

They live in herds interacting with each other.

Unless we can get this down in such a way that we can do many different individuals at a time, you're still just going to have one generation to start with, and that just seems kind of unfair.

WILLIAMS: Although we may never see a mammoth, George's efforts to identify and make more resilient animal genes may have a hidden benefit.

SHAPIRO: This technology, the ability to take genes from the past, put them into species that are alive today, has tremendous potential as a new tool for conservation.

Many of the endangered species and populations have very little genetic diversity and that means that they have very little ability to adapt to rapid climate change, or if a disease comes in, and wipes out most of the individuals who are there.

We can use this technology to help species that are on the brink of extinction today.

But what about us?

We've known for decades that mistakes in our own DNA-- sometimes just the switching of a letter or two-- can lead to life-threatening problems.

For example: an "A" instead of a "T" on just one of our genes causes sickle cell disease, a lifelong blood disorder.

So, is it possible to harness new technologies to rewrite our own genetic code?

Could we use this power to save lives?

♪ ♪ Doctors and researchers have been trying to do this for decades, but with limited success.

Dr. David Williams of Boston Children's Hospital has participated in several gene therapy trials that invariably ended in disappointment.

DAVID WILLIAMS: We saw a real need for this technology to be developed.

People were then disappointed-- including scientists-- when the hype didn't get realized.

To make matters worse, in 1999, 18-year-old Jesse Gelsinger entered a trial for a genetic liver condition.

He only had a mild form of the disease.

But, tragically, the gene therapy ended up killing him.

♪ ♪ This set the field back enormously and it's taken a long time for the field to recover from those setbacks.

CHRISTINE DUNCAN: This is the family we just met this morning.

He's seven years old, but wasn't diagnosed until August.

WILLIAMS: Today, Dave Williams heads a new gene therapy trial that aims to cure a devastating childhood disease...

So he's had febrile seizures since he was eight months old.

WILLIAMS: ...a heartbreaking killer called cerebral adrenoleukodystrophy, or A.L.D., and the stakes couldn't be higher.

♪ ♪ Brian Rojas and his mother Lillianna are just about finished trimming their Christmas tree.

But Brian's brother Brandon cannot join them.

Three years ago, the two boys were inseparable; their family full of love and joy.

Are you ready?

WILLIAMS: Now at age nine, Brandon still gets the love, but A.L.D.

is devastating his mind and body.

All right.

WILLIAMS: He can do nothing for himself anymore.

WILLIAMS: Adrenoleukodystrophy is a genetic disease, and it's what we call X-linked, which means it occurs mostly in boys.

And the typical history that we hear from families is that they have a perfectly terrific young boy who, at the age of five or six, suddenly begins to have developmental problems.

LILLIANA ROJAS: Brandon started with drooling, and we thought that it was because he lost his front tooth and we didn't think anything else of it.

And little by little he started losing his vision.

DUNCAN: They may have change in their vision.

They may have change in their hearing.

They have change in their ability to communicate or speak with the family.

And it all ends up ultimately with complete devastation and death.

WILLIAMS: Dr. Christy Duncan has watched the inexorable decline of many A.L.D.

boys because of a mutation on a gene called ABCD-1 that affects micro-glial cells in the brain.

DUNCAN: These are cells in the brain that are responsible for maintaining a healthy environment around some of the neurons.

And so what you'll see over time is inflammatory lesions in the brain.

WILLIAMS: On MRIs we can see these lesions rapidly increase over time as the disease destroys the brain.

Unless you know there is A.L.D.

in your family, the disease comes as a complete shock.

HEATHER COOKSON: It's heartbreaking to find out that, unknowingly, I passed this gene and, ultimately, disease to my children.

Heather Cookson's son Jerry is 12, older brother Ricky, 14.

Ricky was eight when persistent headaches convinced Heather to insist he get an MRI.

HEATHER: They found a lesion in Ricky's brain during that MRI.

We just thought it was headaches.

Never thought it was going to be a life-changing disease that he was going to have.

WILLIAMS: Children like and Ricky can often be saved with a blood stem cell transplant.

These cells originate in bone marrow and can become all blood cell types.

But why new blood cells stop the progress of A.L.D.

in the brain is somewhat mysterious.

DUNCAN: This is a disease of brain cells.

These are not the same cells and so it can be hard to understand why on earth that works.

WILLIAMS: For his transplant to work, Ricky needs a good genetic match-- like his little brother Jerry.

But Jerry also carried the faulty gene, so could not donate.

Fortunately, Ricky found an unrelated matching donor and after the transplant and chemotherapy, he is now doing fine.

But by the time Brandon Rojas was diagnosed, his A.L.D.

had progressed too far to even try a transplant.

And the news hit hard.

LILLIAN: I couldn't accept the fact that they said there's no cure.

We... I-I-I couldn't accept that.

♪ ♪ And that's when my whole world just fell down (voice breaking): and I didn't know how to react.

DUNCAN: It's terrible.

It's a tragedy.

And the only-- even if you can call it-- sort of bright spot of that tragedy-- his younger brother Brian was identified because of the older brothers' disease.

LILLIANA: Say hi, Brian.

Hi.

Sí!

WILLIAMS: It wasn't guaranteed that having the bad gene would give Brian the deadly form of the disease.

But Lilliana was worried.

LILLIANA: We were hoping he was fine.

We thought, you know, "Please, God, don't let him have the same."

"He became a hero, Dr. Steven..." WILLIAMS: But about a year later, a small lesion appeared on Brian's MRI.

Worse, there were no matching donors for an immediate transplant and his A.L.D.

was progressing by the day.

So when a new gene therapy trial opened up, Lilliana jumped at the opportunity.

One of the things that the doctor said was, "We can save him."

Do you want to go up there?

WILLIAMS: Heather Cookson also learned that her younger son Jerry-- like his older brother Ricky-- had developed A.L.D.

Follow my finger with your eyes.

HEATHER: I got hit with a ton of bricks after his MRI.

♪ ♪ WILLIAMS: But Jerry would soon join Brian Rojas, and 15 other boys, in a gene trial that could save their lives And Jerry Cookson was up for the challenge.

Oh, here?

Therapy begins by collecting stem cells from the boys' blood, then taking them to a clean room where the genetic engineering begins.

The doctors need to insert a healthy version of the gene into the boys' stem cells.

To do this, they rely on a virus that's incredibly adept at invading cells-- H.I.V.

The lethal virus has been altered so it can't make anyone sick.

But it's still able to enter cells and do what virus's always do-- insert its DNA into the host cell.

Only this time, the DNA carries the healthy gene that will hopefully stop the spread of A.L.D.

These viruses sort of say to the cell, "these are your genes, you start producing proteins based on my genetic makeup."

WILLIAMS: Researchers have been editing with viruses for decades, and they're still relying on them for human gene therapy while the newer CRISPR editing is being perfected.

As their cells are being engineered, the boys undergo intense chemotherapy, to make room in their bone marrow for their new stem cells to grow.

Then, it's time for reinfusion, and hope for success.

NURSE: Nice job.

♪ ♪ JERRY: I started chemotherapy, ten days after that, on May 19th I got my cells back into me.

And it's really kind of anticlimactic when you think about it.

WILLIAMS: But Jerry could not feel what was going on inside his body.

The new stem cells multiplied and began circulating in his blood stream.

As they reached his brain, some changed into new glial cells-- now with the healthy gene.

But would this be enough to stop the progress of the disease?

(cheering) After three months Jerry Cookson was released from the hospital and is showing no A.L.D.

symptoms.

♪ ♪ Of the 17 boys who entered the trial, 15 completed the therapy and so far all are doing fine.

JERRY: So I think it's kind of cool that I'm like one in like 16 or 17 people that did this treatment.

And it's a new treatment that could change a lot of other people's lives.

He has been stable, he's in school, he plays soccer, he is perfect.

WILLIAMS: And for the therapy team, this has been the experience of a lifetime.

DUNCAN: I truly feel so incredibly lucky to be at this end of it.

We're finally able to take the fruits of years and years of people's work and treat these boys.

They are going to school and they are living proof of what science can do and it is really remarkable.

HEATHER: We're extremely lucky.

There are some families out there that aren't as lucky as our family.

BRIAN (off-screen): He wore the black costume.

WILLIAMS: For the Rojas family, the end of the trial is bittersweet.

Since Brian received gene therapy, he is healthy and seems to be headed for a normal life, while his brother Brandon is slipping away.

But to Lilliana, Brandon is a hero.

LILLIANA: Because of Brandon, Brian was diagnosed early.

Brandon saved his little brother.

WILLIAMS: A new gene therapy decades in the making saved Brian Rojas.

Could this be a sign we've turned the corner on gene therapy cures?

WILLIAMS: It is literally going to be hundreds of diseases that we'll now be able to approach.

LILLIANA: Very good, nice job.

WILLIAMS: The future of genetic therapy is actually here.

♪ ♪ WILLIAMS: For anyone touched by genetic disease, new breakthroughs could not come quickly enough.

And many hope genetic engineering could go even further.

But if we can fix mistakes in someone's DNA, could we do that even before they were born?

(heartbeat murmuring) We have the ability to alter the DNA inside human embryos, and in the germline cells that make them.

The big question is-- should we?

And why does even talking about this so controversial.

(giggling) CAPLAN: I think the driving fear of the germ line engineering, fixing things across generations, is the slippery slope.

A lot of people would say, "Yeah, okay.

"You want to go out and fix Tay-Sachs disease "that kills people?

"Hooray.

"You want to fix deafness?

"You want to get rid of short stature?

"Where does that all end?

"Aren't we going to wind up doing things like, 'I want my kid to be stronger, smarter, faster'?"

WILLIAMS: In other words, editing embryos not to cure a disease, but to enhance abilities and make designer babies.

♪ ♪ There's been experimental efforts at curing genetic diseases in embryos.

But the fear this could lead to designer babies is so strong, most countries prohibit it entirely.

And the U.S. government won't fund it.

But are these fears justified?

SHOUKHRAT MITALIPOV: The complexity of how to make designer babies is such a big deal we don't even know what genes or how many genes would make a child taller or smarter.

CAPLAN: It's one thing to say, "I'm going to repair a single error that causes a particular genetic disease."

It's another thing to say, "I gotta insert 500 genes in order to make your memory enhanced."

The whole thing is hard to do.

WILLIAMS: But our genetic knowledge is increasing and it certainly seems possible that one day we will be able to design our babies.

CAPLAN: In a competitive market society you see people showing up at IVF clinics saying, "You know, we're having trouble conceiving, "but as long as I'm here, "could I get a 6-foot-7 Ukrainian mathematician donor "because that's what we wanted; red-headed, is that possible?"

Down the road long term are we going to see enhancement or improvement anyway?

Yes.

WILLIAMS: But if we do go down this road, where will it end?

MARCY DARNOVSKY: You know, when we start doing really biologically radical things, we could see some terrible health consequences develop when the child is two years old, 20 years old, or when that child has children of his or her own.

We just don't know what the unintended consequences might be.

And that anybody who would be contemplating using a technology like this should really ask themselves whether it's worth the risk.

♪ ♪ WILLIAMS: The power of genetic engineering to sculpt ourselves and the natural world does bring a burden of risk.

And although Kevin Esvelt is confident his engineered mice will only reduce Lyme disease, and not bring harm to Nantucket's ecosystem, he also knows that absolute certainty and genetic engineering do not go together.

ESVELT: I worry every day that I might be missing something profound about the consequences of what we're developing.

WILLIAMS: At a town hall meeting, Kevin assures residents he will be taking a go-slow approach.

Frankly, what we're talking about here is altering the shared environment.

♪ ♪ WILLIAMS: And that he could halt the experiment if problems appeared.

Most importantly, they would determine if the mice would ever get released here.

To be clear, this project will only move forwards if the community supports it at every step of the way.

WILLIAMS: He tells them he would first perform a field test on an isolated island to check that the new gene is working and the altered mice are causing no problems.

Only then would he propose releasing them on Nantucket.

Once we have those, then... WILLIAMS: But for his new gene to spread throughout the mouse population, he would need to release a lot of engineered mice.

It might mean releasing, say, 100,000 mice on Nantucket.

WILLIAMS: It would take that many to spread the Lyme-resistant gene effectively.

What happens to the actual population, the mouse population itself?

I mean that's just going to keep growing, and growing, and growing.

TELFORD: Actually, no... WILLIAMS: Although residents are concerned by the numbers, Sam Telford assures them the mice population will stay in check.

Something is out there that's regulating them.

Disease is regulating them.

There's a mite, a mange mite that is regulating them.

WILLIAMS: But even one GMO mouse is still alarming for some.

The is rapid, rapid, man-made evolution.

Some people think that genetically modified organisms should never be done.

They think that people like Kevin are playing God.

We don't know what effect it's going to have 15 years, 20 years, 25 years down the line.

WILLIAMS: But Kevin's cautious, open science approach seems to be winning the day.

ESVELT: If you were to run these kinds of experiments the way science is traditionally done-- behind closed doors-- you'd be denying people a voice in decisions intended to eventually affect them.

Devon, why don't you come on down?

WILLIAMS: Islanders have given Kevin the go ahead to engineer the mice.

But with a Nantucket release years away, there are no hard choices for them to make... yet.

So how we doing?

Still, residents here are so fed up with Lyme disease, if the field test does go well, Kevin's grand experiment could go all the way.

And if he stops Lyme here, what diseases would he target next?

Could Kevin and other researchers one day engineer mosquitos to halt the spread of deadly malaria?

ESVELT: If we could just go in there and change the mosquitoes so they can't transmit malaria, or better yet, someday so that they just don't want to bite people, that would be the most elegant solution to a problem.

♪ ♪ WILLIAMS: Kevin Esvelt is walking in the footsteps of those early pioneers who engineered bacteria to make insulin for diabetics.

Today, we have the capacity to alter the genomes of every living thing.

So, the potential rewards-- and the risks-- of genetic engineering have never been greater.

PAUWELS: A few decades ago, the changes we would impose on biology were very much incremental.

They were little steps.

But now we could drastically accelerate the engineering of our genes, our bodies, and even our ecosystems.

(moose bellowing) WILLIAMS: Despite all we can do, there's still one thing we can't do.

JONES-PRATHER: We can't create life.

We can't create a cell from scratch.

We can take an existing cell and we can make so many changes to it that it looks nothing like what it started out as.

But we have to start from something that's already living in order to end up with something that's living.

♪ ♪ WILLIAMS: So right now, we can't make life, but we can radically change it in ways that will impact our own evolution and the future of the planet.

The question is: will we use this power wisely?

♪ ♪ Hey, it's there-- we got something.

WOMAN: The first ever.

NARRATOR: The hunt for the secret ingredients of the universe.

This is a mystery.

MAN: We came up with this bizarre result.

MAN: Most of what astronomers had assumed fell apart.

NARRATOR: The mysterious invisible forces that control the fate of the cosmos.

We have no idea what it is.

Very weird.

I mean, it's Crazy Land.

NARRATOR: "NOVA Wonders."

"What's the Universe Made of?"

Next time.

♪ ♪ ♪ ♪ "NOVA Wonders" is available on DVD.

To order, visit shop.PBS.org, or call 1-800-PLAY-PBS.

"NOVA Wonders" is also available for download on iTunes.

♪ ♪