Re: can scientist clone a person who has been dead for 1000 years? and how?

A good question. How long can you leave a body sitting around before it
becomes impossible to clone somebody from it?

Let's suppose we could successfully get some totally intact cells from that
body. The first thing to realize is that, at the moment, we haven't even
successfully cloned a _living_ human. This is because cloning has a high
failure rate.

Researchers at Seoul National University just cloned a dog. Snuppy, the
clone, was born from one of 1,095 clonal embryos. He was the only one to be
born (apparently) healthy. All the others died, and there's no proof that
Snuppy's going to live a normal lifespan either. So, if we tried to clone a
person, there's a good chance the clone would die, which brings up an
ethical problem. [1]

There are several reasons for this high death rate, but the most likely is
that imprinting prevents it.

We sometimes think of DNA as just being a long sequence of chemical bases -
ATTAGGCAT and so on. But DNA also carries a lot of other information;
proteins and chemicals attached to it can turn specific genes on and off.
Why is this a problem?

When we clone a mammal, we get some cells from its body, remove their
nuclei, and inject those nuclei into eggs that have had their nuclei
removed. Each egg has some chance of successfully developing, and if it
does, it will be genetically identical to the donor, because all of the
donor's DNA is in the injected nucleus. But it will also carry imprints.

Suppose we got a nucleus from a muscle cell. The DNA in that nucleus has
been imprinted so that genes that muscle cells need are transcribed. When
we put it in the egg, it is still a muscle cell nucleus. In order for this
embryo to be capable of producing an entire person, the imprinting on the
DNA has to be erased and replaced with new, embryonic imprints. This can
happen, but it's a longshot, which is why it was so difficult to make Snuppy.

But if we got enough nuclei from the dead body, we might be able to keep
trying until we got a clone. However, getting those intact nuclei is a neat
trick. The nuclei of dead cells rupture, ruining them for injection. It's
possible you could dig out some intact ones from a thousand-year-old
corpse, but unlikely.

Unless the corpse were frozen and well-preserved in ice - then it's hard to
say. Researchers HAVE cloned animals from frozen cells, in fact, so maybe
if you found a thousand-year-old body in ice, you could clone the person.
(A banteng, a cowlike animal, cloned from thirty-year-old frozen cells can
be seen at the San Diego Zoo.) [2]

The question of WHY one would want to clone a thousand-year-old person,
aside from the admitted coolness factor, is a tougher one. The clone would
just be an ordinary person, with no obvious sign of his or her unique
pedigree. Maybe if you wanted to bring back an old royal bloodline?

[1] Vogel, G. The Perfect Pedigree. Science, 309:862 http://www.sciencemag.org/cgi/content/full/309/5736/862b?maxtoshow=&HITS=10&hits=10&RESULTFORMAT=&fulltext=snuppy&searchid=1125978429070_10809&stored_search=&FIRSTINDEX=0&fdate=10/1/1995&tdate=9/30/2005

[2]http://www.cbsnews.com/stories/2003/04/08/tech/main548333.shtml