LINKAGE INFORMATION-CONTENT AND EFFICIENCY OF FULL-SIB AND HALF-SIB DESIGNS FOR GENE-MAPPING

The accuracy of a genetic map depends on the amount of linkage informa tion contained in the data set used for construction of the map. The a mount of linkage information is related to the designs employed for li nkage analysis. The purpose of this study was to provide general formu lations for various genotyping schemes and family structures in order to evaluate the amount of linkage information in a data set. Linkage i nformation content (LIC) was defined as the frequency of fully informa tive gametes, which are gametes from doubly heterozygous parents with known linkage phases. Depending on the design, LIC is based on two gen erations if the parental phases are determined statistically, or three generations if the parental phases are determined genetically. Differ ent schemes were considered in deriving LIC: (1) genotyping of one par ent or two parents, and (2) genotyping of two or three generation fami lies. The LIC for a full-sib design was found to be generally greater than for a half-sib design but requires typing a large number of indiv iduals when at least one locus has only two alleles. The efficiency of the full-sib design is reduced significantly if a sex-specific linkag e map is sought.