Recombination events that span sites within neighbouring gene loci ofNeurospora

Abstract

SUMMARY: Evidence is given thatme-7andme-9are separate but contiguous gene loci.The pattern of polarized recombination throughout theme-7 me-9region indicates the location of a recombinational discontinuity between the knownme-7alleles and the knownme-9alleles.Recombination events may include sites in both genes but such events are not preferentially associated with parental combinations of flanking markers.Recombination events extending into both genes provide an extra criterion for the ordering of the sites within theme-7locus. The order so obtained confirms that deduced from the flanking markers of me⁺recombinants fromme-7×me-7crosses.Inme-7×me-9crosses butnotinme-7×me-7crosses, the map order derived on the assumption that single exchanges are more frequent than apparent triple exchanges is the reverse of that derived from prototroph frequencies. It is concluded that the former criterion is more likely to have provided the correct order and the anomalous prototroph frequencies reflect the polarity of gene conversion withinme-7.