National Geographic: The Incredible Human Body Page #2

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of those letters.

It's elegant in it's simplicity.

The genetic code

has four different chemicals;

we substitute A, C, G, and for those.

We attach

four different color dyes -

one color for each of

the letters of the genetic code.

It's like just solving

a jigsaw puzzle,

only the jigsaw puzzle has, in

our case, 27 million pieces...

So it came in a very big box

and there was no picture

on the cover.

Narrator:
Putting the pieces

of this puzzle together

has provided knowledge

that will enhance the quality

of human life -

and perhaps even extend it.

Coffey:
We're at the

very fundamental first steps

in a very powerful force.

There's some relationship

between aging and our genes.

So if we can control

those genes,

will we be able

to extend the aging process?

Well, it's distant stuff,

but probable.

Knowing the human genome,

and mapping up how it changes,

is a major step forward

in understanding

the making of this wonderful

human body that we've got.

Through the history of time,

the DNA sequence

has been marching down

through generation after

generation of your relatives,

and now it continues

in your offspring.

Narrator:
Overnight, DNA from Inez's eggs

and Darryl's sperm unite,

and 13 of the 27 eggs

show the telltale dimple

that indicates success.

It's working.

With exquisite grace,

one cell becomes two,

two become four; each duplicates

the original, unique DNA.

The enchanted progression

of cell division continues.

For five days,

the embryos are monitored.

Finally, the division

creates masses of cells,

known as blastocysts,

and any one

of these blastocysts

may become a part

of the Pearson family.

Prosser:
This embryo here...

If you look at the outer shell

on the center embryo,

it's very thin.

The embryo is getting ready

to hatch out of it's shell.

It's a very nice blastocyst.

The inner cell mass is going

to become the embryo itself -

what you normally think of

when you think of a baby...

Arms, head, legs, toes, fingers.

And, actually,

this inner cell mass

is where you find

the embryonic stem cells,

which are very much in the

center of the genetic revolution

that's going on right now.

Narrator:
Embryonic stem cells stand

in the vanguard of human life.

These magical

all-purpose cells

will eventually transform into

every cell type in the human body.

This extraordinary potential

of stem cells

has made isolating them one

of the holy grails of science,

Although a controversial one.

Dr. John Gearhart is at the

forefront of that achievement.

Gearhart:
These cells

have two properties.

One is that if you

keep them in the dish,

under certain

culture conditions,

they will continue to form

more cells like themselves.

So you can grow a room full

of these embryonic stem cells

and they are undifferentiated

cells; they all look alike.

If you take some

of these cells, though,

and you put them out

in different kinds

of growth conditions,

these cells are capable

of forming all the cell types

that are present

in the human body.

What we are looking at here

are heart muscle cells

that are beating as a tissue.

Narrator:
Once these were stem cells

with uncharted destinies.

Dr. Gearhart has directed their

development into heart cells,

now able to beat

in perfect synchrony.

Gearhart:
It's always been

the dream of humankind

that someday we'd be able

to replace tissues in the body

that were either damaged

or diseased or simply worn out.

But we really never had the

starting material to do this.

Now we have in the laboratory,

in our dishes, growing nicely,

virtually all the cell types

that are present

in the human body.

Coffey:
They make a "you."

A stem cell can make you.

That's pretty powerful!

And I can

control this stem cell

And understand

everything about it?

Now we're set up to answer

one of the first

and basic questions

about how a human is made.

Sauer:
As we hoped,

we have very well-formed

And ready-to-transfer

type of blastocysts.

of growth in the lab,

Inez's embryos

are ready for implanting.

She is shown what might turn out

to be her first baby picture.

Sauer:
Now, with

embryos of this quality,

if I put in three,

the chance of multiple birth

may be as high as 40

to 50 percent, usually twins.

If that makes you overly nervous,

then I would suggest

putting in two,

which still gives you a very

good rate, but less multiples.

What do you think

about all that?

Ummmm... I think we'll

go with the two.

Okay. Okay.

So we'll do two...

Inez:
At first, I was

just going to do two.

I said, "Well, if one doesn't

make it, then one will live."

And, you know, at the last minute

I was sitting here thinking was,

I said, "Well,

it's not that much either."

I mean, for the amount of things

that we had gone through,

to just do one was not

a very smart idea to do.

And then we started

talking about it, I said,

"Wow, two's

not that great either."

So maybe...

I'll do the three.

Sauer:
Now you wanna do...

Yeah, I'll do

the three. Yeah.

I'll put in

that new order for you.

Okay.

Bob, she wants

the three now.

Narrator:
The three embryos

are put into a single catheter,

and guided onto the lining

of Inez's uterus.

Sauer:
There it goes...

So our placement is very good.

Real well... This is what

you hope for when you start.

I really think it's a 50-50

chance for her at this point.

Whether or not

she'll get pregnant,

we'll find out in about 10 days.

Inez:
I didn't get,

like, really, really excited

because they said, you know,

there is a chance

that it might not work,

might not be successful,

and we don't want you

to really get

your hopes up too high,

so I just kept it like that.

Narrator:

science has done it's best,

but it will be

a long 10 days for Inez...

Five viable blastocysts...

three now offering Inez

the chance to be a mother.

Scott:
Does that look right?

Not really, does it?

Okay, what about

Narrator:
Much of what we know about

the way the human body works

emerges when it is

in need of repair.

Scott Toenies, a veteran

and football coach

in rural North Dakota,

is the victim

of debilitating seizures

that have led

to the frightening discovery

of a massive brain tumor.

Two months ago, Scott's tumor

began growing rapidly,

as did the frequency

and severity of his seizures.

Often he would pass out.

If left untreated, Scott may

have less than a year to live.

Scott:
I had

three seizures in three weeks.

And all of a sudden,

it was like, "whoa..."

"We need to do something."

Narrator:

Scott and his wife Lisa

travel to

the renowned Mayo Clinic

in Rochester, Minnesota,

where high-risk brain surgery

has been recommended.

The brain is a greedy organ.

While Scott's brain makes up

just two percent of his body weight,

it consumes 20 percent

of the oxygen his body uses.

Floating within his skull,

it's two hemispheres

contain 100 billion cells

and the eager connections

between these cells

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