Maximum-likelihood estimation of gene location by linkage disequilibrium

Area of Science:

• Population Genetics
• Genetic Mapping
• Disease Gene Discovery

Background:

• Linkage disequilibrium (D) measures the non-random association of alleles at different loci.
• D can theoretically assist in pinpointing the chromosomal location of disease-associated genes.
• Accurate estimation of D is crucial for genetic mapping studies.

Purpose of the Study:

• To derive likelihoods for the value of linkage disequilibrium (D).
• To assess the utility of D in determining the map position of disease genes.
• To evaluate the influence of population size (N) and recombination fraction (c) on D estimation.

Main Methods:

• Derived likelihoods for D based on observed haplotype counts and population parameters (Nc).
• Computed likelihoods explicitly for two-locus systems with heterozygote superiority.
• Employed computer simulations for general cases, assuming constant population size and selective pressures or neutrality.

Main Results:

• The likelihood function for D was found to be generally flat.
• The likelihood showed minimal dependence on the degree of selection at the loci.
• Estimates of D did not provide precise information regarding gene map positions.

Conclusions:

• Precise genetic mapping of disease genes using linkage disequilibrium estimates is challenging.
• The flatness of the likelihood function limits the resolution achievable with this method.
• Further refinement of methods for disease gene localization may be necessary.