Life without sex is conjectured to lead to extinction because of the way DNA naturally accumulates mutations so asexual species, lacking such a means of DNA repair, are thought to accrue harmful mutations over time that can help bring an end to a species. However, asexual bdelloids have proven quite prolific diversifying into at least 400 species.
To see how bdelloids might have prospered without sex and its DNA repair mechanisms, scientists zapped them with gamma rays to shatter their DNA into many pieces but even at five times the levels of radiation that all other animals are known to endure, bdelloids were able to continue reproducing.
Scientists believe that at some point the entire genome of the first bdelloid got duplicated giving it four copies of each chromosome and thus of each gene. The bdelloids kept most of its extra genes over time, and "we believe they have kept most of their duplicate genes because they are serving as templates for DNA repair," says evolutionary biologist David Mark Welch.
A better understanding of how bdelloids live without sex could shed light on how sex evolved in the first place.
Photo: Photo: "Scanning electron micrographs showing morphological variation of bdelloid rotifers and their jaws" by Diego Fontaneto Creative Commons All PLoS content published under CC-BY license
No comments:
Post a Comment