Looking to Bacteria for Clues
IN HIS NEWS FOCUS STORY “ON THE ORIGIN of sexual reproduction” (5 June, p. 1254), C. Zimmer highlights the importance of the phylogenetic perspective championed by John Logsdon, but by considering only eukaryotes he overlooks an important bacterial clue to the evolution-of-sex puzzle.
Until recently, bacteria were thought to be sexual; they have well-characterized processes that cause recombination of chromosomal alleles, and these parasexual processes were assumed to have evolved for recombination in the same way as meiotic sex in eukaryotes. However, a more critical analysis of the genes responsible for the parasexual processes suggests that they did not evolve for sex after all. Instead, the chromosomal recombination they cause appears to arise as unselected effects of related processes, the evolutionary functions of which are well established (1).
The fact that bacteria lack genes evolved for recombination indicates that meiotic sex must have evolved in eukaryotes to solve a problem that bacteria don’t have. Bacteria apparently get whatever recombination they need by accident—why do eukaryotes need so much more?
ROSEMARY J. REDFIELD
Department of Zoology, University of British Columbia, Vancouver, BC V6T 3Z4, Canada. E-mail: redfield@interchange.ubc.ca
Now I really have to blog about eukaryogenesis...
ReplyDeleteTC-S (2002 (or 2003) Heredity) has this thing on sex where he seems to think (at the time):
- cells would fuse together during crappy environmental conditions to conserve resources;
- during 'good' times, the plasmodial unions would break apart; sometimes, a nucleus would inherit twice the ploidy level it should have, and meiosis may have evolved as a way of correcting that
- diploidy often happens during cyst stage, where it may be advantageous for the organism to have two copies of the genome when exposed to harsh radiation during resting stage (don't know how much I buy that at the moment)
- together, and with the byproducts of replication repair machinery, this became sex.
I probably butchered that, need to re-read the paper, but it's quite interesting to think about... but I'm supposed to be imaging right now >_>
Congrats on the six sentences! Should have a Sentence Index, ie how many sentences you have in Nature+Science+top journal in own field. Since 'quantifying' one's research ability is such a great idea!
Cheers,
-Psi-
LOL - right below Patrick's piece too!
ReplyDeleteI really admire this, I mean it really looks interesting..Keep sharing..!
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