KRULWICH: And to show you
the true power of this molecule
we're going to start
with one atom deep inside
and we pull back and you see it
form its As and Ts and Cs and Gs
and the classic double spiral.
  And then starts
the mysterious process
that creates a healthy new baby.
  And the interesting thing
is that every human baby--
every baby born-- is 99.9%
identical in its genetic code
to every other baby.
So the tiniest differences
in our genes
can be hugely important--
can contribute to differences
in height, physique
maybe even talents, aptitudes--
and can also explain what can
break, what can make us sick.
  Cracking the code of those
minuscule differences in DNA
that influence health
and illness
is what the Human Genome Project
is all about.
  Since 1990, scientists
all over the world
in university
and government labs
have been involved
in a massive effort to read
all three billion As, Ts,
Gs and Cs of human DNA.
They predicted it would take
at least 15 years.
  That was partly because in
the early days of the project
a scientist could spend years--
an entire career--
trying to read just a handful
of letters in the human genome.
It took ten years to find
the one genetic mistake
that causes cystic fibrosis; another ten years to find the
gene for Huntington's disease; 15 years to find
one of the genes
that increase the risk
for breast cancer...
one letter at a time...
painfully slowly...
SCIENTIST:
One, two, three...
KRULWICH: Frustratingly prone
to mistakes...
SCIENTIST:
Cs in a row...
KRULWICH:
And false leads.
We asked Dr. Robert Waterston,
a pioneer in mapping DNA
to show us the way
it used to be done.
WATERSTON: The original ladders
for DNA sequence...
we actually read
by putting a little letter
next to the band
that we were culling
and then writing those down
on a piece of paper
or into the computer after that.
Uh, it's horrendous.
KRULWICH: And we haven't
mentioned the hardest part.
This here,
magnified 50,000 times
is an actual clump
of DNA, chromosome 17.
Now, if you look inside,
you will find, of course
hundreds of millions
of As and Cs and Ts and Gs.
But it turns out that
only about one percent of them
are active and important.
These are the genes that
scientists are searching for.
So somewhere
in this dense chemical forest
are genes involved in deafness,
Alzheimer's, cancer, cataracts.
But where?
This is such a maze,
scientists need a map.
But at the old pace, that
would take close to forever.
WATERSTON:
A C, and then an A...
KRULWICH:
And then came the revolution.
  In the last ten years the entire
process has been computerized.
That cost hundreds
of millions of dollars.
  But now instead of decoding
only a few hundred letters
by hand in a day
together these machines can do
a thousand every second
and that has made
all the difference.
  MAN: This is something that's
going to go in the textbooks.
Everybody knows that.
Everybody, when the genome
project was being born
was consciously aware
of their role in history.
Getting the letters out
is... has been described
as "finding the blueprint
of a human being"
"finding a manual
for a human being"
"finding the code
of a human being."
What's your metaphor?
Oh, golly gee,
I mean, I... I...
you can have very
highfalutin metaphors
for this kind of stuff.
This is basically
a parts list.
Right?
Blueprints and
all these fancy...
it's just a parts list.
It's a parts list
with a lot of parts.
If you take an airplane,
a Boeing 777...
KRULWICH:
Yeah.
LANDER: I think it has,
like, 100,000 parts.
If I gave you a parts
list for the Boeing 777
in one sense, you'd know a lot.
You'd know 100,000 components
that have got to be there--
screws and wires and, you know
rudders and things like that.
On the other hand
I bet you wouldn't know
how to put it together.
And I bet you wouldn't
know why it flies.
Well, we're in the same boat.
We now have a parts list.
That's what the Human
Genome Project is about
is getting the parts list.
If you want
to understand the plane
you have to have the parts list
but that's not enough to
understand why it flies.
But, of course,
you'd be crazy
not to start
with the parts list.
  KRULWICH: And one reason
it's so important
to understand all those parts--
to decode every letter of the
genome-- is because sometimes
out of three billion
base pairs in our DNA
just one single letter
can make a difference.