a1 Botany School, University of Cambridge
An inverted segment in one of the chromosomes of Sordaria brevicollis has been found to have a marked effect on recombination within a gene in another chromosome. There are two effects on the intragenic recombination pattern, namely, a change in the polarity of recombination and a change in the frequency of parental and recombinant outside markers. The results support the idea that a mechanism exists for cancelling crossovers shortly after they have been formed as a means of controlling their number.
(Received November 15 1971)
p1 Present address: Institut für Allgemeine Mikrobiologie, Universität Bern.
p2 Present address: Department of Genetics, University of Edinburgh.