A robust test for assortative mating

Testing for random mating in human populations is difficult due to confound ing factors such as ethnic preference and population stratification. With H LA, the high level of polymorphism is an additional problem since it is rar e for couples to share the same haplotype. Focus on an ethnically homogeneo us population, where levels of polymorphism at HLA loci are more limited, m ay provide the best situation in which to detect non-random mating. However , such populations are often genetic isolates where there may be inbreeding to an extent that is difficult to quantify and account for. We have develo ped a test for random mating at a multiallelic locus that is robust to stra tification and inbreeding. This test relies on the availability of genotypi c information from the parents of both spouses. The focus of the test is on families where there is allele sharing between the parents of both spouses , so that potential spouses could share an allele. Denoting the shared alle le at the locus of interest by A, then under the assumption of random matin g, heterozygous parents AX should transmit allele A equally as frequently a s allele X to their offspring. When there is positive (negative) assortativ e mating, A will be transmitted more (less) often than X. The power of the test has been computed in a number of situations. Data on high resolution H LA haplotypes from the Hutterite population were reinvestigated by the prop osed test. The test detects significant negative assortative mating when th e parental origin of the shared haplotype is taken into account.