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Re: Nucleated RBCs
This can be found at http://www.sciencenow.org/html/970408b.htm
Tuesday, 8 April 1997, 6:30 p.m.
No Go for Reconstituted Dino
Scientists have failed to find any trace of DNA in insects trapped in
amber some 30 million years ago. The findings, reported in the 23 April
Proceedings of the Royal Society, may sound a death knell for efforts to
salvage a snip of ancient DNA to help unravel evolutionary relationships
between living species and their ancestors.
In the past few years, several groups of scientists have claimed to have
extracted genetic material from insects preserved in amber, or from
fossilized tree resin. None of these results has been independently
replicated, though, and critics have long suspected that the "ancient"
DNA was actually contaminants from people handling the amber or other
modern DNA sources.
Now a new research project has produced what many regard as a
definitively negative result. Evolutionary biologist Jeremy Austin and
his colleagues at the Natural History Museum in London bent over
backward to avoid contamination. That included getting a spanking-new
lab, with never-before-used instruments, at a cost of $240,000. For
their analyses, the researchers used samples from the same amber
collections that provided a termite and a bee from which scientists
claimed in 1992 to have isolated DNA. But after 2 years, Austin's group
reports having found nary a wisp of DNA.
That casts serious doubts on the original reports, as well as a 1993
claim by scientists at California State Polytechnic University who said
they had extracted DNA from a 125 million year old Jurassic Park-age
weevil. Many scientists doubted these claims because cells and their DNA
generally start degrading within hours of death. Only in dry and frozen
places such as the Tyrolean Alps, where the 5000-year-old "Ice Man" was
found, have body tissues and DNA been successfully preserved.
Molecular biologist Svante Pääbo of the University of Munich, one of the
scientists who isolated the Ice Man's DNA, says that he is "not
surprised at these negative results from amber." But Austin says he and
his colleagues had expected to be able to replicate the earlier results.
"We had high hopes at the beginning," he says, "so these negative
results are disappointing."