Consanguinity and the sib-pair method: an approach using identity by descent between and within individuals

Area of Science:

• Genetics
• Biostatistics
• Population Genetics

Background:

• Linkage analysis in related individuals, like sibs, uses marker allele identity.
• Identity by descent (IBD) of alleles in affected inbred individuals provides linkage information for recessive diseases.

Purpose of the Study:

• To extend the sib-pair linkage analysis method to consanguineous populations.
• To develop a new linkage test utilizing condensed identity coefficients for enhanced information from IBD patterns and allelic identity within sib pairs.
• To evaluate the performance of the new test against the classical chi-squared test.

Main Methods:

• Extension of the sib-pair method to consanguineous populations using condensed identity coefficients.
• Development of a novel chi-squared test for linkage analysis.
• Comparison of the proposed test with the classical chi-squared test based on IBD sharing distributions.
• Analysis of inbreeding's impact on expected IBD sharing proportions in sib pairs.

Main Results:

• The proposed chi-squared test demonstrates superior power in detecting disease-susceptibility (DS) loci for sib pairs from first-cousin matings.
• The new test is particularly effective for models with common and incompletely penetrant DS alleles, relevant to multifactorial diseases.
• Ignoring inbreeding in linkage analysis when it exists inflates Type I error rates.

Conclusions:

• The extended sib-pair method and new chi-squared test enhance linkage detection in consanguineous populations.
• The proposed method is more powerful than the classical approach, especially for complex genetic disease models.
• Accurate accounting for inbreeding is crucial to avoid increased false positive rates in linkage tests.