GENES IN NEUROSPORA THAT SUPPRESS RECOMBINATION WHEN THEY ARE HETEROZYGOUS

[摘要] Genes that suppress recombination when heterozygous have been found distributed as a polymorphism in wild and laboratory populations of Neurospora crassa . Three alleles, ssE, ssS and ssC , are associated, respectively, with the three wild types Emerson, St. Lawrence 74A and Costa Rica A . It is proposed that ss (synaptic sequence) genes modulate recombination by determining the pairing closeness of DNA duplexes in the vicinity of the nit-2 locus. When heterozygous, ss suppresses recombination 2- to 20-fold within the nit-2 locus, which it adjoins, but crossing over in intervals flanking nit-2 is not affected. The magnitude of suppression depends upon the ss alleles involved, and ss acts multiplicatively with rec-1 ; together, these genes modulate recombination within the nit-2 locus over a range exceeding 100-fold. The ss effect is not attributable to gross chromosomal rearrangement, but could be due to small inversions or insertions, such as transposable elements.

[学科分类] 医学（综合）