Heterogeneity in recombination frequencies inNeurospora crassa

Abstract

The available data on heterogeneity in centromere distances for a number of loci in several linkage groups are analysed and interpreted. When the crosses are grouped according to wild-type ancestry, heterogeneity is eliminated in any one group except those which consist of backcrosses or intercrosses. Abbott 4 and 12 are shown to be the source of the heterogeneity while Lindegren and probably Chilton wild strains give consistent, homogeneous distances. In a cross between Abbott 12 and Lindegren wild-types, the centromere distances of mt and asco show heterogeneous values between the spore pairs in an ascus indicating that significantly different distances are genetically determined and that the factors concerned show segregation. The genetic determination differs in the various wild strains; the data suggest that at least three factors are involved. In random spore analyses heterogeneity is present in recombination frequencies between linked markers either proximal or distal to their centromere. The mechanism by which heterogeneity in the data might arise is discussed. To obtain homogeneous data it is suggested that all markers used should be repeatedly backcrossed to the Lindegren wild-type.

Two linkage groups inCoprinus lagopus

“…Frost (1961) has analysed the consequences of using different stocks of Neurospora crassa and has shown how different genetic backgrounds may have profound effects on recombination frequencies within a given interval. The difficulty in determining the relative positions of ad-5 and chol-2 is most likely due to the fact that they were mutants induced in different wild-type stocks.…”

Genetic control of recombination in Schizophyllum commune: specific and independent regulation of adjacent and non-adjacent chromosomal regions

“…The " fine " controls can be recognised in various organisms as heterogeneity in recombination values between the same markers, due to differences between the genotypes involved (the "genetic background "). This type of genetic control has been explored in two fungi in particular, namely Xeurospora crassa (Frost, 1961;Lavigne and Frost, 1964;Smith, 1966Smith, , 1968Catcheside, 1968) and Schizophllum commune (Simchen, 1967;Stamberg, 1968, and personal communication; Simchen and Connolly, 1968) and in both marked variation has been found between different "wild-type " strains. In the latter we have shown that recombination both between Ac.…”

Genetic control of recombination in Neurospora crassa

“…That similar polygenic control systems operate in fungi has been suggested from findings of extreme heterogeneities in crossing over frequencies for the same markers, when parents with different origins are used (FROST 1961;STADLER and TOWE 1962;NAKAMURA 1966;SIMCHEN and STAMBERG 1969).…”