Narrator: This is Science Today. A genetic
mutation linked to the most common form of childhood
leukemia appears to form in the womb. Joseph Wiemels,
an epidemiologist at the University of California,
San Francisco, says there seems to be at least two
genetic changes that cause acute lymphoblastic leukemia
- one that occurs before birth and another, during
Wiemels: The first thing we'd like to know
is, is this very common or does every individual
who gets the mutation before birth get leukemia?
And what our research suggests is that no, they
don't necessarily get leukemia, they have to have
the second event - the deletion of the other chromosome.
Narrator: Studies suggest this second mutation
may result from an abnormal response to common,
childhood infections, whereas the initial mutation
seems to be the result of a developmental accident,
not exposure to an environmental mutagen.
Wiemels: Really what we're trying to do is
define the natural history of leukemic clone. Find
out when it starts and what happens to it all up
to that point. By being able to trace when these
genetic events happen, we can then devise preventative
Narrator: For Science Today, I'm Larissa Branin.