Intron size and natural selection

Article Abstract:

It has been established that larger introns of Drosophila melanogaster arise preferentially in regions of low recombination. This is consistent with large introns having a damaging effect. There is no significant connection between recombination rate and intron size within large introns, so whatever prompts this relation must have an equal impact against all large introns, regardless of their absolute size. Natural selection in Drosophila selects against large introns and very short introns, as both tend to arise in regions of low recombination where selection is not as effective.

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Design of single-layer beta-sheets without a hydrophobic core

Article Abstract:

The engineering of OspA variants containing larger single-layer beta-sheets was undertaken by duplicating a beta-hairpin unit within a beta-sheet. The extended single-layer beta-sheets were formed and were stable. Interactions within the beta-hairpin unit and those between adjacent units, not involving the formation of a hydrophobic core, can specify and stabilize the single-layer beta-sheet structure.

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Protamine wars

Article Abstract:

Whyckoff and colleagues have reported on the accelerated evolution of genes encoding protamine proteins, which are linked to male reproduction. They argue that such rapid evolution is driven by sexual selection. There is the supposition that altered protamines affect sperm morphology, and the statistics show that changes in protamines are not simply random.

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