The recombination, repair and modification of DNA.

Abstract This article is an overview of the author's involvement in theoretical and experimental research on genetic recombination and DNA repair, and also on the enzymic modification of cytosine in DNA to 5-methyl cytosine. It includes the history of the discovery of the central intermediate in genetic recombination at the DNA level, and the repair of mismatched bases. These explain the major features of genetic fine structure. The first repair and recombination defective mutants in any eukaryote were isolated in the smut fungus Ustilago maydis . The hypothesis that DNA methylation has a role in gene expression in higher organism is now supported by abundant evidence. Direct evidence that gene silencing in mammalian cells is causally related to DNA methylation has been obtained.