DNA profiling has become an extremely powerful tool in forensics and is increasingly
used in criminal trials. If the bodies of Mallory and Irvine are found, scientists
hope to use these new, cutting-edge techniques to convincingly identify the climbers
using just a shred of evidence. Gill Rysiecki works for Cellmark Diagnostics near Oxford in the U.K., a lab that specializes in just such testing.
NOVA: What sort of cases do you work on at Cellmark?
RYSIECKI: In the early days, DNA testing was very expensive and very tricky.
You actually needed a great deal of DNA to get a result. So it was really saved
for the most serious cases: rapes, murders, that sort of thing. It's now a lot
quicker, easier, and less expensive to do. You can test tiny amounts of tissue
and get a result. So this has really opened up the field, and police can use it
for all sorts of things.
A lab technician analyzes samples of DNA.
NOVA: If the team
on Everest were to find the remains of what they thought to be Mallory or Irvine,
how would you test for their identity?
RYSIECKI: In this case, it's more like a paternity test that we would
be doing, because we'd be comparing samples with living relatives to see whether
we could establish a link. The key principles about DNA that we use in this
analysis are the following. Each person has his or her own unique DNA. If I
looked at your DNA it would be unique and different than mine. The only people
that have the same DNA are identical twins. So, within an individual's body,
all of the cells contain exactly the same DNA. When it comes to inheritance,
we each inherit half our DNA from each parent. So, in the Mallory case, what
we're looking for is some sample from the body that contains DNA. The difficulty
in this case is that the death occurred such a long time ago, and DNA does get
broken up and degraded quickly by bacteria.
NOVA: What makes you think you'll still be able to do a good analysis,
given how old the samples will be?
RYSIECKI: If you can store DNA in a freezer, it will keep indefinitely.
And I guess being on the top of Everest is quite close to that sort of condition.
What we're hoping is that because of the cold, and because of the desiccation,
the DNA will be well preserved. If they can bring some muscle, or a tooth, or
a bit of bone—I'm very conscious that they don't want to desecrate these bodies
in any way—but if they can bring some tissue down it doesn't have to be very
much at all. What we'll then do is compare the DNA pattern we find there with the
DNA patterns of living relatives. We would get blood samples from the relatives
and then compare the patterns. If you give us DNA from George Mallory, then John,
his son, would have half of the DNA pattern that George would have. If there are
no similarities, then we know that John is not the son of the man they've found
on the mountain.
A child inherits half of its DNA from each parent. In this result the
child has two bands, one inherited from its mother, the other from the father.
NOVA: How has DNA testing improved in recent years?
RYSIECKI: There are now three generations of DNA testing. The main aim
has been to make them more sensitive in terms of being able to detect smaller
and smaller amounts of DNA. The push for that has been from the forensic
applications. We have all three types of testing going on here. The very first
type of testing is the most powerful, but it needs a lot of DNA. The latest
type of testing requires very little DNA, it's very sensitive, and it's very
quick. But it's not nearly as powerful as the first one.
NOVA: What is the process of DNA profiling?
RYSIECKI: In all three generations of DNA testing, what you have to do
is extract the DNA from the sample, and that involves breaking open the cell.
We usually do that with a detergent, which releases all the contents of the
cell. There are proteins in there, there are lipids, and there is DNA. We
purify the DNA away from the other components. The system we're most likely
to use then is called the Polymerase Chain Reaction (PCR). That takes the
DNA that you have and makes copies of it. So if you only have a small amount
of DNA, by going through this PCR 20 or 30 times, you can amplify the amount
of DNA you have until there is enough there to really analyze.
NOVA: Is there a specific area of the DNA that you focus on?
RYSIECKI: When we are doing this PCR test, what we are doing is looking
at seven or eight different areas in the DNA. And these are areas that are very
variable in the population. While I said earlier that your DNA is unique to you,
and my DNA is unique to me, actually, most of it is the same from one person to
the next. We have masses of DNA in each of our cells—if I took just one of your
cells, and if I stretched out all the DNA, there would be about a meter in there,
so there really is a lot of it, and most of it is the same. But there are areas in
the DNA which are "hypervariable," and that means there are lots of different
forms in the population. And these are the pieces that are useful for what we
Could cutting-edge DNA profiling, only several years old, answer the 75-year mystery of Mount Everest?
So we would focus in on eight or nine of such areas of variability. And in each of
these areas, the person we're looking at has two copies, one that they inherited
from their mother and one from their father. So if we look at eight or nine of
these areas, and we look at a man and his son, we'd find that half of the pieces
in the man had been passed on to his son, so we should see 50 percent or more
concurrence between the two. Of course, the other half would come from his mother.
NOVA: How long would it take to get a definite result?
RYSIECKI: That very much depends on the sample that comes from Everest.
It may be that we try and we can't get anything from it—the DNA that was in
there is completely gone, it's been degraded into tiny pieces that are of no use.
If that's the case, then that's it, there's nothing more we can do. Or it may be
that we can get DNA from it, but we have to try two or three times. So it's hard
to project. Two or three weeks would be a reasonable time-scale in which to
get an answer.
Back to The Search
Photos courtesy of Cellmark Diagnostics.
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