Sporadic, Global Linkage Disequilibrium Between Unlinked Segregating Sites

Area of Science:

• Population Genetics
• Genomics
• Statistical Genetics

Background:

• Genetic indistinguishability, or perfect linkage disequilibrium (LD) between unlinked loci, can arise from demographic, genetic, or stochastic factors.
• This phenomenon complicates genotype-phenotype association studies by hindering the precise localization of causal alleles.
• Previous research has not thoroughly explored this from a theoretical standpoint or with large, dense whole-genome data.

Purpose of the Study:

• To theoretically model and simulate the prevalence of genetic indistinguishability between unlinked loci.
• To identify the primary determinants of genetic indistinguishability.
• To quantify the occurrence of genetic indistinguishability in model organisms.

Main Methods:

• Derivation of a theoretical model for the prevalence of genetic indistinguishability.
• Simulation studies to verify the theoretical model's accuracy.
• Analysis of large, dense whole-genome polymorphism data from three model organisms.

Main Results:

• Sample size and minor allele frequency are major determinants of perfect LD between unlinked loci.
• Demographic factors, such as deviations from random mating, also significantly influence genetic indistinguishability.
• Thousands of genetically indistinguishable variant pairs with moderate frequencies were identified in model organisms.

Conclusions:

• Genetic indistinguishability is a significant phenomenon in population genetics with implications for association studies.
• Understanding the conditions that promote genetic indistinguishability is crucial for accurate allele localization.
• The study provides a framework for predicting and interpreting genetic indistinguishability in genetic data.