Aging: Lifespan and the evolution of somatic mutation rates.

A new study finds an inverse correlation between lifespan and somatic mutation rate in mammals. This suggests an evolutionary relationship between aging and somatic mutation rates, perhaps mediated by selection against noncancerous selfish lineages.

Changes to the mtDNA copy number during yeast culture growth.

We show that the mitochondrial DNA (mtDNA) copy number in growing cultures of the yeast increases by a factor of up to 4, being lowest (approx. 10 per haploid genome) and stable during rapid fermentative growth, and highest at the end of the respiratory phase. When yeast are grown on glucose, the onset of the mtDNA copy number increase coincides with the early stages of the diauxic shift, and the increase continues through respiration.

Application of simultaneous selective pressures slows adaptation.

Beneficial mutations that arise in an evolving asexual population may compete or interact in ways that alter the overall rate of adaptation through mechanisms such as clonal or functional interference. The application of multiple selective pressures simultaneously may allow for a greater number of adaptive mutations, increasing the opportunities for competition between selectively advantageous alterations, and thereby reducing the rate of adaptation. We evolved a strain of that could not produce its own histidine or uracil for ~500 generations under one or three selective pressures: limitation of the concentration of glucose, histidine, and/or uracil in the media.

Mutational Load and the Functional Fraction of the Human Genome.

The fraction of the human genome that is functional is a question of both evolutionary and practical importance. Studies of sequence divergence have suggested that the functional fraction of the human genome is likely to be no more than ∼15%. In contrast, the ENCODE project, a systematic effort to map regions of transcription, transcription factor association, chromatin structure, and histone modification, assigned function to 80% of the human genome.

The fitness cost of mismatch repair mutators in Saccharomyces cerevisiae: partitioning the mutational load.

Mutational load is the depression in a population's mean fitness that results from the continual influx of deleterious mutations. Here, we directly estimate the mutational load in a population of haploid Saccharomyces cerevisiae that are deficient for mismatch repair. We partition the load in haploids into two components.