Re: News: No sex for 40 million years? No problem for 1 organism

John Harshman wrote:
Ye Old One wrote:

No sex for 40 mln years? No problem for 1 organism
Reuters
By Michael Kahn Reuters - 2 hours 10 minutes ago

http://uk.news.yahoo.com/rtrs/20071011/thl-uk-sex-survival-b2e59e8_1.html

LONDON (Reuters) - One microscopic organism has thrived despite
remaining celibate for tens of millions of years thanks to a neat
evolutionary trick, researchers said.

Asexual reproduction has allowed duplicate gene copies of the
single-celled creatures -- called bdelloid rotifers -- to become
different over time.

Ah, science journalism. Rotifers are not single-celled.

And it should seem obvious that if meiosis never happens, homologous
chromosomes will diverge to produce an effectively haploid genome.
What's the surprise?

What, so that each homologous pair of chromosomes (assuming we started as diploid) drifts so far apart that they're no longer homologous?


This gives the rotifers a wider pool of genes to help them adapt and
survive, the researchers said in the journal Science.

"It is like having a bigger tool kit," Alan Tunnacliffe, a molecular
biologist at the University of Cambridge, said in a telephone
interview. "You can do the same job but better."

Other researchers had shown the translucent, waterborne creatures
could survive for 40 million years without sexual relations.

The question, Tunnacliffe said, was how the creatures found in pools
of water accomplished this feat without the gene-swapping made
possible by sexual reproduction.

"Sexual reproduction is supposed to be a good thing in evolution," he
said on Thursday.

"So when you come across an organism like the bdelloid, which hasn't
engaged in sexual reproduction for tens of millions of years, you
begin to question why sex is important."

Every species of plant and animal that reproduces sexually has pairs
of genes nearly identical to each other, with one of each pair coming
from the mother and father.

These creatures get around that problem with the evolutionary trick
that allows their genes to drift apart and evolve on their own,
Tunnacliffe said, after using molecular cloning techniques.

"No sex means the genes can evolve in different directions," he said.
"It is like you have a bigger gene pool to select from for different
functions in evolution."

The theory of natural selection says sex mixes up the genes to cope
with unexpected changes in a treacherous world.

Some genetic changes are good and boost survival, for example against
new strains of disease, but others lead to conditions like cystic
fibrosis in humans.



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