ESTIMATION OF LINKAGE IN TRISOMIC INHERITANCE

Based on F-2 families derived from selfed F-1 trisomic plants we have developed a genetic model to estimate linkage relationships between pa irs of loci located on the extra chromosome. Genotypic frequencies of each class expected in a trisomic F-2 family have been calculated and the maximum-likelihood equations for recombination-fraction estimation have been derived for a variety of genetic situations. Morton's test of homogeneity was used to compare recombination fractions estimated b etween loci exhibiting trisomic segregation to those obtained in famil ies where the same loci showed Mendelian segregation. This method has been applied to an analysis of morphological, isozyme and RAPD data fr om faba bean (Vicia faba L.).