RECOMBINATION AND GENE FLUX CAUSED BY GENE CONVERSION AND CROSSING-OVER IN INVERSION HETEROKARYOTYPES

A theoretical analysis of the effects of inversions on recombination a nd gene flux between arrangements caused by gene conversion and crossi ng over was carried out. Two different mathematical models of recombin ation were used: the Poisson model (without interference) and the Coun ting model (with interference). The main results are as follows. (1) R ecombination and gene flux are highly site-dependent both inside and o utside the inverted regions. (2) Crossing over overwhelms gene convers ion as a cause of gene flux in large inversions, while conversion beco mes relatively significant in short inversions and in regions around t he breakpoints. (3) Under the Counting model the recombination rate be tween two markers depends strongly on the position of the markers alon g the inverted segment. Two equally spaced markers in the central part of the inverted segment have less recombination than if they are in a more extreme position. (4) Inversions affect recombination rates in t he uninverted regions of the chromosome. Recombination increases in th e distal segment and decreases in the proximal segment. These results provide an explanation for a number of observations reported in the li terature. Because inversions are ubiquitous in the evolutionary histor y of many Drosophila species, the effects of inversions on recombinati on are expected to influence DNA variation patterns.