Centrometric linkage in autosomal trisomies

A detailed description of the cytological mechanisms leading to autosomal trisomy shows that the proportion of trisomics carrying three alleles from three of their grandparents is bound to be greater than zero for any locus anywhere on a trisomic chromosome. The likelihood method used to estimate this proportion in pedigree data can be applied to the detection of linkage, or to investigations on the origin of trisomy when linkage is known.