Molecular Biology of Meiosis: Synapsis-Associated Phenomena

Abstract

In tracing the metabolism of nuclear DNA during meiosis we have identified two groups of DNA sequences, each displaying a distinctive pattern of behavior during meiotic prophase. One group, which will be referred to as zygotene DNA (“zygDNA”), is coordinated in most of its activities with chromosome pairing. The other group, referred to as pachytene DNA (“PDNA”), is coordinated in its behavior with what we believe to be the process of crossing-over. Each group has been and continues to be identified by its respective mode of replication during zygotene and pachytene, well after the apparent completion of the premeiotic S-phase. The theme of this chapter is that chromosomes of at least the larger eukaryotic genomes have evolved certain DNA sequences that are specifically addressed to particular chormosomal needs during meiosis. In this chapter we focus on the zygDNA sequences because of their apparent relationship to chromosome pairing. We have no direct evidence that this is indeed the case, but we do know that the behavior of zygDNA during meiotic prophase provides strong evidence for its playing an important role in the process. Our description of that role is necessarily conjectural and our interpretation of various findings are slanted in favor of the conjecture.