Fig. 2. Changes in CAG repeats during gene conversion. Following HO induction of gene conversion between a chromosomal leu2 locus and a URA3-containing plasmid containing leu2::(CAG₉₈), individual colonies were isolated. Cells lacking the URA3-marked plasmid were selected on 5-FOA and DNA was analyzed by Southern blots. The examples shown are from wild-type cells. Lane 1: uninduced control cells; lane 4: non-homologous recombination event giving rise to partial deletion of the LEU2 locus; lanes 2, 5, 11: gene conversion that faithfully copies CAG₉₈ into the chromosomal locus; lanes 3, 6, 7, 8, 12, 15: gene conversion that yields a deletion in the recipient; lane 14: gene conversion that leads to an expansion of CAG repeats in the recipient; lanes 9, 10, 13: gene conversion in which the recipient contained heteroduplex DNA, producing a colony with two different-sized CAG repeats of equal intensity.