The analysis of close linkage in large families

In large families, if two closely linked loci both have rare alleles and several distant members are ascertained through one having rare alleles at both loci, simple estimates of their recombination fraction are possible. This information is free from errors due to both reduced penetrance and erratic paternity. Simple estimates based on counting will often have high efficiency and limited bias. Some problems of linkage analysis between loci with codominant expression in complete three generation families are also considered. The omission of individuals of uncertain genotype at the test locus will be more efficient than their inclusion.