Sex Is Not About Promoting Genetic Variation, Researchers Argue
ScienceDaily (July 7, 2011) — Biology textbooks maintain that the main function of sex is to promote genetic diversity. But Henry Heng, Ph.D., associate professor in WSU's Center for Molecular Medicine and Genetics, says that's not the case.
Heng and fellow researcher Root Gorelick, Ph.D., associate professor at Carleton University in Canada, propose that although diversity may result from a combination of genes, the primary function of sex is not about promoting diversity. Rather, it's about keeping the genome context -- an organism's complete collection of genes arranged by chromosome composition and topology -- as unchanged as possible, thereby maintaining a species' identity. This surprising analysis has been published as a cover article in a recent issue of the journal Evolution.
"If sex was merely for increasing genetic diversity, it would not have evolved in the first place," said Heng. This is because asexual reproduction -- in which only one parent is needed to procreate -- leads to higher rates of genetic diversity than sex.
For nearly 130 years, traditional perceptions hold that asexual reproduction generates clone-like offspring and sexual reproduction leads to more diverse offspring. "In reality, however, the relationship is quite the opposite," said Heng.
And not only does asexual reproduction lead to higher rates of genetic diversity, it also is two times more efficient than sexual reproductio.
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SEX REDUCES GENETIC VARIATION: A MULTIDISCIPLINARY REVIEW
Root Gorelick1,2,3, Henry H. Q. Heng4,5
Article first published online: 20 NOV 2010
DOI: 10.1111/j.1558-5646.2010.01173.x
© 2010 The Author(s). Evolution© 2010 The Society for the Study of Evolution.
Evolution
Volume 65, Issue 4, pages 1088–1098, April 2011
Abstract
Keywords: Adaptation; evolutionary genomics; genetic variation; genome theory; sex; variation
For over a century, the paradigm has been that sex invariably increases genetic variation, despite many renowned biologists asserting that sex decreases most genetic variation. Sex is usually perceived as the source of additive genetic variance that drives eukaryotic evolution vis-à-vis adaptation and Fisher's fundamental theorem. However, evidence for sex decreasing genetic variation appears in ecology, paleontology, population genetics, and cancer biology. The common thread among many of these disciplines is that sex acts like a coarse filter, weeding out major changes, such as chromosomal rearrangements (that are almost always deleterious), but letting minor variation, such as changes at the nucleotide or gene level (that are often neutral), flow through the sexual sieve. Sex acts as a constraint on genomic and epigenetic variation, thereby limiting adaptive evolution. The diverse reasons for sex reducing genetic variation (especially at the genome level) and slowing down evolution may provide a sufficient benefit to offset the famed costs of sex.
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NOTA DESTE BLOGGER:
Atenção autores de livros-texto de Biologia do ensino médio: não é mais para aparecer em seus livros que o sexo promove a variação genética, capice???
