(Laughter)

When you are in a relationship, when do you say,

"I love you," for the first time?

How do you know you are in love?

When do you define the relationship?

When do you make it 'Facebook official'?

(Laughter)

We all know the symptoms of love:

the butterflies in your stomach, your hands getting clammy,

so nervous, you are terrified,

but you cannot wait for more.

There's a lot going on when you fall in love.

You thought it was just a bunch of heartache and money.

Your brain goes through all kinds of changes.

It gets flooded with oxytocin, the love chemical.

Falling in love is physiological.

On the other hand, since the time you could walk,

you've heard stories about love from everyone.

Is the ability to fall in love genetically programmed

or were you conditioned to fall in love?

Is it nature or is it nurture?

We do not know.

What exactly do we mean by "Nature vs. Nurture"?

By "Nature" we mean things that are genetically programmed,

passed down from generation to generation,

apart from a fluke mutation once in a while.

By "Nurture" we mean things that are learnt,

or a product of your environment, like riding a bike,

or maybe staying in the sun too long and getting skin cancer.

How about the ability to deal with stress?

Is that genetically programmed, or a product of your environment?

How about gender identity? Nature or Nurture?

How about the ability to annoy people?

(Laughter)

Don't you just want to ask that annoying person at work:

"Were you genetically programmed to be that way?"

(Laughter)

"Or do you actually practice that in front of the mirror all day?"

(Laughter)

Some traits are not nature and not nurture

but something different all together: epigenetic.

Epigenetics literally means a layer above your genetics.

If your genetics is the hardware,

your epigenetics is the software, or the operating system.

Your epigenetics allows the environment to change your DNA.

The most famous example of epigenetics is the response to stress.

A group in Montreal used rats to go after the specific question:

"If you are an attentive mom, does that affect the DNA of your children?"

They looked at two populations of rats.

In population number 1

the mothers were very nurturing, licking and grooming their pups.

These baby rats actually have the royal treatment.

Mom's cuddling them all the time, tying their shoes,

driving them to soccer practice every day.

(Laughter)

These baby rats had it made.

They looked at the DNA of these baby rats, and the DNA looked fine.

In population number 2 these mothers were not very nurturing.

No licking, no grooming, no cuddling. Not very attentive.

They looked at the DNA of these baby rats

and they found strange marks on that DNA,

and those marks were positioned precisely at the stress response gene.

In fact, these baby rats couldn't deal with any stress at all.

And that behavior persisted for their whole lifetime.

For kicks, they decided to look at the grandkids' DNA.

And the grandkids' stress response gene was turned off too.

How could that possibly be?

How can a mother nurturing her pups change their DNA?

Let's think about what DNA is.

DNA is a molecule

that's very thin and very long.

There is enough DNA in your body

to wrap around the Earth 2.5 million times.

How can all that DNA be squeezed into your body

in such an organized way to control everything?

Your DNA is threaded

around tiny, microscopic spools,

trillions and trillions of these spools.

Here we can see DNA in all its glory, atom for atom.

It's wrapped around molecular spools,

called histones, in blue.

At first, the stress response is turned off.

But when our baby rats are being hugged and cuddled,

serotonin is released in their brains.

Serotonin turns on a light switch,

called lysine number 4.

This is chemically modified, or acylated,

triggering the spools to unwind, unwrapping the DNA,

exposing the stress response part to the cell.

So our baby rats are happy and healthy.

You can think of it like a garden hose.

Imagine a garden hose a mile long,

here in this theater, floating in the air.

Do you know those garden hose spools, the plastic ones,

to store the garden hose?

Imagine thousands of those spools winding and unwinding,

turning genes on and off with exquisite precision.

Somehow, these spools have special powers.

They know what is happening all around the cell.

They can turn the genes on and off

at just the right times, at just the right moments.

They are so exquisite,

they can take an egg cell to an embryo to a newborn baby.

So our molecular spools are winding and unwinding, controlling everything,

like the maestro of a big dance, or better yet, a DJ.

If our hose were actually the color green and glowing,

then we'd actually have a real rave party in here.

Like, you know —

♪ Boots and pants and boots and pants and boots and pants and boots and pants ♪

(Laughter)

OK. (Laughter) (Applause)

So that was Epigenetics 101;

a big rave party in your cells,

where DNA and socialization get all tangled up together.

How about gender identity?

Was I born a girl or did I become one?

This question shattered

almost every romantic relationship that I've been in.

You see, I am a woman who happens to be transgender.

For years I struggled,

until I finally found the courage to be who I really am.

(Applause) (Cheers)

If you think love is complicated,

imagine what it is like for me;

about as complicated as that DNA molecule we're looking at.

Luckily, both of my parents nurtured me all the time,

so I have plenty of serotonin stored up to deal with stress

and to be here, on this stage, coming out.

(Applause)

I've been following in the footsteps

of Laverne Cox, Geena Rocero and Janet Mock.

Back when I was in therapy, my therapist mentioned:

"If you could identify the genetic basis of gender dysphoria,

it would be a real breakthrough."

She actually used the word rockstar,

and who does not want to be a rockstar?

At the time, I was working in the field of RNA.

This is DNA's molecular cousin.

So, I sat down and I googled,

"RNA and gender identity."

There was only one hit, "steroid receptor RNA activator."

This helps estrogen do its thing.

It also directly binds the sex reversal factor.

I went to my postdoc, Irina.

"I've got this RNA molecule and no one has really heard of it.

It is so big, it's going to be almost impossible to study.

How about this for your new project?"

"Well, let's go for it!"

To set the stage, remember our molecular spools?

Always in the know.

Somehow they knew what was happening,

always in right place, at the right time.

How do these spools know what's going on?

Groups around the world are racing to figure this out.

Many think that it could be RNA.

You see, RNA molecules can sense their environment.

They can bind drugs and vitamins.

If our big RNA molecule were highly structured,

it could actually talk to those spools,

telling them what's happening all around the cell.

Like: "Yikes, it's freezing in this part of the cell."

Or: "Mmm, caffeine in this part of the cell."

Or: "Run for your life. It's a sperm molecule."

(Laughter)

On the other hand,

if our big RNA had no structure, like a bowl of spaghetti,

then all that it could say to the spool would be gobbledygook,

like: "Bo tosh beer job blue Dee ray ahh cock kook nay."

(Laughter)

OK, that wasn't gobbledygook.

That was the Klingon language from Star Trek, but you get the idea.

(Applause)

In the end, this is what we found.

Our big RNA molecule had structure everywhere.

25 helices in all, all kinds of interactions.

This is just a baby step,

but it's a proof of principle that RNA could be the answer.

RNA molecules have been shown to have links to Alzheimer's and autism,

and epigenetic effects, in general, have strong ties

to addiction, depression, schizophrenia.

Ten years ago, we couldn't fathom how these could be.

Now, we are taking the first steps.

Some day, we might understand love,

which brings us back to our question:

how do you know you are in love?

We can't answer this yet,

but maybe in the future, when your kids ask you:

"How do you know you're in love?"

you can answer: "It's simple.

When lysine 4

on histone 3

at the oxytocin receptor gene is chemically modified.

That's how you know you're in love."

(Laughter) (Applause)