The effect of deleterious mutations on neutral molecular variation

Area of Science:

• Population genetics
• Molecular evolution

Background:

• Deleterious mutations are constantly introduced by mutation.
• Selection against these mutations can impact linked neutral genetic variation.
• This phenomenon, known as background selection, is crucial for understanding genome evolution.

Purpose of the Study:

• To derive approximate formulas for the reduction in genetic variability due to background selection.
• To investigate the impact of background selection on various population genetic statistics.
• To explore the influence of recombination and mating systems on background selection.

Main Methods:

• Derivation of approximate analytical formulas.
• Computer simulations to validate theoretical predictions.
• Analysis of factors like recombination frequency, outcrossing rate, and population size.

Main Results:

• Background selection causes a reduction in nucleotide site diversity and the number of segregating sites.
• The reduction is an exponential function of the deleterious mutation rate and is sensitive to recombination and outcrossing.
• Certain statistics, like mean time to loss and number of segregating sites, are less sensitive unless population size is very large.

Conclusions:

• Background selection is a significant factor reducing molecular variation, particularly in low recombination genomic regions.
• Observed patterns of reduced variation in regions like Drosophila centromeres and selfing plant populations may be partly explained by background selection.
• The findings provide a theoretical framework for interpreting patterns of genetic variation in diverse organisms.