Mechanisms of Meiotic Gene Conversion, or “Wanderings on a Foreign Strand”

INTRODUCTION Over the last decade and a half, studies in organisms amenable to tetrad (or octad) analysis have provided a reasonably complete descriptive inventory of intragenic recombination (Fogel et al. 1979; Nicolas 1979; Rossignol et al. 1979; Sang and Whitehouse 1979). This paper aims to provide an overview of the relevant data. At the same time it attempts a synthesis of the new information in the expectation that a scaffold will emerge from which testable molecular hypotheses concerning generalized and intragenic recombination can be constructed. A comprehensive review of the literature concerning meiotic recombination will not be attempted. Much of the data have been cogently summarized in texts by Esser and Kunnen (1967), Whitehouse (1969), Grell (1974), Kushev (1974), Catcheside (1977), Fincham et al. (1979), Stahl (1979b) and in several critical reviews by Emerson (1969), Mortimer and Hawthorne (1969), Fogel and Mortimer (1971), Radding (1973), Hotchkiss (1974), Hastings (1975), Esposito and Esposito (1977), Pukkila (1977), Resnick (1979), Stahl (1979a), and Petes (1980b). Here, we approach the problem of intragenic meiotic recombination or recombinagenic events within short DNA segments by considering four questions. What is the phenomenon of gene conversion? What are the methods that can be employed to study this phenomenon? What are the salient features of the conversion process? Can methodologies of recombinant DNA technology be adapted to advance the analysis of intragenic recombination from the genetic level to the molecular level? We may begin by asking, What is meiotic gene conversion? In organisms subject...