Parameters in gene conversion: An algebraic analysis of the hybrid DNA model at thegraylocus ofSordaria fimicola.

Abstract

SUMMARYWe have extended previous algebraic analyses of aberrant segregation at thegraylocus ofSordaria fimicola(Whitehouse, 1965; Emerson, 1966; Fincham, Hill & Reeve, 1980) to the more complex situation where aberrant segregations are detected in three factor crosses involving two flanking markers. This algebra has been applied to sevengrayalleles which have been extensively characterized for their pattern of gene conversion and postmeiotic segregation by Kitani & Olive (1967). It is based on seven major types of aberrant segregation which can be distinguished in the presence of flanking markers spanning the converting site, and allows us to use up to six parameters to describe hDNA formation and mismatch repair. We present solutions which predict a spectrum of aberrant segregation fitting the experimental data at theP> 0·05 level for six of the seven alleles tested. They are consistent with the following properties of hDNA at thegraylocus: (1) the single stranded DNA transferred during hDNA formation has always the same chemical polarity. (2) hDNA is mostly, if not entirely, symmetric, and its probability of formation is constant over the whole gene. (3) Disparity in aberrant segregation is mostly, if not entirely due to disparity in mismatch repair.