Action of rec-3 on recombination near the amination-i locus of neurospora crassa

The rec-3⁺ gene, which strongly reduces allelic recombination in am-I, has shown no effect on non-allelic recombination in an 8 map unit interval spanning am-i Allelic recombination in the gul-I locus, less than 0·3 map units distal to am-I, is also apparently not affected. However, selected recombinants between am-I and gul-I show differences dependent on rec-3⁺ constitution. These can be attributed to reduced levels of crossing over and conversion in am-I in the presence of rec-3⁺. This highly localized action of rec-3⁺ can be accounted for if many specific sites exist in this region at which recombination may be initiated. However, a product of rec-3⁺ would recognize only one specific site, closely proximal to am-I, and repress the initiation of recombination at this site.