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: email@example.com
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