Journal of Theoretical Biology
Volume 175, Issue 4, 21 August 1995, Pages 583-594
doi:10.1006/jtbi.1995.0167 Contamination of the genome by very slightly deleterious mutations: why have we not died 100 times over?
Alexey S. Kondrashov
f1
f1Section of Ecology and Systematics, Cornell University, Ithaca, NY 14853, U.S.A.
Received 21 October 1994;
accepted 3 February 1995. ;
Available online 2 May 2002.
Abstract
It is well known that when s, the selection coefficient against a deleterious mutation, is below ≈ 1/4Ne, where Ne is the effective population size, the expected frequency of this mutation is ≈ 0.5, if forward and backward mutation rates are similar. Thus, if the genome size, G,i n nucleotides substantially exceeds the Ne of the whole species, there is a dangerous range of selection coefficients, 1/G< s< 1/4Ne. Mutations withswithin this range are neutral enough to accumulate almost freely, but are still deleterious enough to make an impact at the level of the whole genome. In many vertebratesNe≈ 104, while G≈ 109, so that the dangerous range includes more than four orders of magnitude. If substitutions at 10% of all nucleotide sites have selection coefficients within this range with the mean 10−6, an average individual carries ≈ 100 lethal equivalents. Some data suggest that a substantial fraction of nucleotides typical to a species may, indeed, be suboptimal. When selection acts on different mutations independently, this implies to high a mutation load. This paradox cannot be resolved by invoking beneficial mutations or environmental fluctuations. Several possible resolutions are considered, including soft selection and synergistic epistasis among very slightly deleterious mutations.
f1 E-mail: ask3@crux2.cit.cornell.edu.
f1 E-mail: ask3@crux2.cit.cornell.edu.
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NOTA DESTE BLOGGER:
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NOTA DESTE BLOGGER:
Esta pesquisa da Kondrashov é para ser considerada cum grano salis tendo em vista as mutações filtradas pela seleção natural serem, entre n mecanismos evolucionários, consideradas como o fiat evolutio na origem das espécies. Por que nós não morremos pelo menos umas 100 vezes???
Fui, cada vez mais cético das especulações transformistas de Darwin. E tem gente que espera que eu volte para os braços de Darwin. Por que, hein???
