Estimation of linkage disequilibrium from conditional haplotype data: application to beta-globin gene cluster in American blacks.

Simple estimators of gene frequencies and linkage disequilibria are proposed when haplotype data are available from four parental chromosomes of a child (or fetus) for whom genetic counseling is sought for a disease condition. The method is illustrated with restriction site polymorphisms associated with sickle-cell anemia (Hb-beta S) gene as surveyed in genetic counseling data from American blacks. The method suggested here is shown to be useful in testing for the significance of interactions of site-specific variations of any order in the chromosomal region assayed.