title: The control of gene conversion properties and corresponding-site interference: the effects of conversion control factor 5 on conversion at locus w9 in Ascobolus immersus.
abstract: The controls of various aspects and parameters of gene conversion at locus w-9 in the fungus Ascobolus immersus were investigated, along with positive and negative corresponding-site interference in meiotic chromatid pairing. When conversion control factor 5 alleles A and B were heterozygous, conversion frequencies at the closely linked target locus w9 were reduced to 3%, compared with 10.7% when A or B was homozygous, through effects on hybrid-DNA (h-DNA) formation parameters gamma1 and gamma2. In different ways, not related to whether ccf-5 alleles were homozygous or heterozygous, ccf-5 also affected parameters relating to the relative frequencies of asymmetric and symmetric h-DNA, the frequency with which the chromatid bearing the wild-type allele was the invading chromatid in asymmetric h-DNA, and h-DNA correction parameters for the frequency and direction of correction of mispairs. Corresponding-site interference is interference between the two pairs of non-sister chromatids of a bivalent in h-DNA formation at exactly corresponding sites. This interference was positive in the high conversion frequency crosses homozygous for ccf-5 alleles but was strongly negative in the low conversion frequency crosses heterozygous for ccf-5 alleles, through differential effects on parameters gamma1 and gamma2. Models of chromatid pairing are discussed.
authors.affiliation: Department of Biological Sciences, Imperial College of Science, Technology and Medicine, London, UK. b.lamb@ic.ac.uk
authors.forename: Bernard C
authors.initials: BC
authors.lastname: Lamb
authors.forename: Ghulam
authors.initials: G
authors.lastname: Shabbir
mesh_terms: D001203:Ascomycota / Q000235:genetics*; D002874:Chromosome Mapping; D003434:Crossing Over, Genetic; D004271:DNA, Fungal / Q000235:genetics; D005785:Gene Conversion; D006579:Heterozygote; D006720:Homozygote; D011995:Recombination, Genetic
chemical_list: D004271:DNA, Fungal