Abstract
Recombination occurs in both meiotic and mitotic cells. In many ways, these recombination events appear quite different. For example, gene conversion events in meiosis are generally accompanied by crossing-over for about half of the time, while mitotic gene conversions involve exchanges much less often. There are also significant differences in gene conversion tract length in meiosis and mitosis. Moreover, from studies on various recombination-defective mutations, it is also clear that there are mutants that specifically block meiosis without having any significant effect on mitotic events and vice versa. The chapter focuses on the substrates of these enzymes: homologous sequences undergoing gene conversion and crossing-over. In the yeast Saccharomyces cereuisiae, recombination events can be induced at such high frequency, with sufficient synchrony, that intermediate steps in recombination can be isolated and the specific predictions of various models of recombination can be tested. The chapter considers both general recombination events (intragenic and intergenic recombination on both normal and artificial chromosomes) and several well-studied site-specific recombination events [FLP-mediated crossing-over in 2μ-DNA, ω conversion in mitochondria, and mating-type (MAT) switching].