The relation of reduplication, recombination, synapsis and chromosome coiling

Abstract

It has long been believed that partially paired chromosomes observed at early meiotic prophase represent synapsis caught in the act and that crossing over must follow or accompany this stage. In contradiction to this it has often been suggested that certain observations (e.g. the occurrence of 3: 1 ratios from individual tetrads of yeast,NeurosporaandAspergillus) are most easily explained if it is assumed that crossing over occurs at the time of reduplication which in turn is now thought to occur during the premeiotic interphase (Taylor, 1957). Another phenomenon, which has been reported inNeurospora, Drosophilaand bacteriophage, and apparently must be fitted into any successful model of recombination, is localized negative interference.