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Timothy McDougald



Posts: 1008
Joined: Dec. 2006

(Permalink) Posted: July 17 2008,07:00   

Two more, both open access from PNAS:

Modular networks and cumulative impact of lateral transfer in prokaryote genome evolution:
Quote

Abstract

Lateral gene transfer is an important mechanism of natural variation among prokaryotes, but the significance of its quantitative contribution to genome evolution is debated. Here, we report networks that capture both vertical and lateral components of evolutionary history among 539,723 genes distributed across 181 sequenced prokaryotic genomes. Partitioning of these networks by an eigenspectrum analysis identifies community structure in prokaryotic gene-sharing networks, the modules of which do not correspond to a strictly hierarchical prokaryotic classification. Our results indicate that, on average, at least 81 ± 15% of the genes in each genome studied were involved in lateral gene transfer at some point in their history, even though they can be vertically inherited after acquisition, uncovering a substantial cumulative effect of lateral gene transfer on longer evolutionary time scales.


and

A germ-line-selective advantage rather than an increased mutation rate can explain some unexpectedly common human disease mutations

Quote
Abstract

Two nucleotide substitutions in the human FGFR2 gene (C755G or C758G) are responsible for virtually all sporadic cases of Apert syndrome. This condition is 100–1,000 times more common than genomic mutation frequency data predict. Here, we report on the C758G de novo Apert syndrome mutation. Using data on older donors, we show that spontaneous mutations are not uniformly distributed throughout normal testes. Instead, we find foci where C758G mutation frequencies are 3–4 orders of magnitude greater than the remaining tissue. We conclude this nucleotide site is not a mutation hot spot even after accounting for possible Luria–Delbruck “mutation jackpots.” An alternative explanation for such foci involving positive selection acting on adult self-renewing Ap spermatogonia experiencing the rare mutation could not be rejected. Further, the two youngest individuals studied (19 and 23 years old) had lower mutation frequencies and smaller foci at both mutation sites compared with the older individuals. This implies that the mutation frequency of foci increases as adults age, and thus selection could explain the paternal age effect for Apert syndrome and other genetic conditions. Our results, now including the analysis of two mutations in the same set of testes, suggest that positive selection can increase the relative frequency of premeiotic germ cells carrying such mutations, although individuals who inherit them have reduced fitness. In addition, we compared the anatomical distribution of C758G mutation foci with both new and old data on the C755G mutation in the same testis and found their positions were not correlated with one another.


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Church burning ebola boy

FTK: I Didn't answer your questions because it beats the hell out of me.

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