Detection of genome similarity as an exploratory tool for mapping complex traits.

For one- and two-trait-locus models, we show that the lod score based on affected relative pairs or trios is a monotonically increasing function of the genome similarity measured by the proportion of alleles shared identical by descent (IBD) conditional on observed marker data. These results can be generalized to multitrait-locus models. Thus, we can use conditional probability of genes shared IBD as a tool to reveal chromosomal segments that are likely to harbor the genes underlying the complex traits.