Constrained disequilibrium values and hitchhiking in a three-locus system

Area of Science:

• Population genetics
• Molecular evolution
• Genomics

Background:

• Positive selection on new alleles can cause hitchhiking, increasing linked allele frequencies and creating linkage disequilibrium.
• Linkage disequilibrium, the non-random association of alleles at different loci, can be influenced by selection.
• Identifying loci under selection is crucial for understanding evolutionary processes.

Purpose of the Study:

• To investigate the reliability of the constrained disequilibrium values (CDV) method for detecting selection.
• To assess the ability of CDV to distinguish between selected and neutral loci.
• To evaluate the utility of CDV in screening for hitchhiking events.

Main Methods:

• Utilized simulation and analytical methods to examine the CDV approach.
• Analyzed differences in normalized pairwise disequilibrium values for two- and three-locus systems.
• Applied the CDV method to a microsatellite data set from human chromosome 6.

Main Results:

• CDV may not always distinguish effectively between selected and neighboring neutral loci.
• CDV rarely indicates selection in neutral haplotypes with moderate to large 4Nc.
• Constrained disequilibrium values suggested selection in a region of human chromosome 6, including HLA-A and MOG loci.

Conclusions:

• The CDV method is a useful tool for screening genomic regions where hitchhiking is a plausible hypothesis.
• While CDV may not pinpoint selected alleles precisely, it aids in identifying potential regions of positive selection.
• The study highlights the relationship between hitchhiking and linkage disequilibrium, offering avenues for further evolutionary research.