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Recombination block in the Spore killer region of Neurospora

1987; NRC Research Press; Volume: 29; Issue: 1 Linguagem: Inglês

10.1139/g87-022

1480-3321

Joseph L. Campbell, Barbara C. Turner,

Photosynthetic Processes and Mechanisms

Spore killers Sk-2 K and Sk-3 K are chromosomal meiotic drive factors in Neurospora. In heterozygous crosses, ascospores not contining the Spore killer die. Sk-2 K and Sk-3 K , which differ in killing specificity, were found to be associated with suppression of recombination in a centromere-spanning region of linkage group III, and investigation of that recombination block is reported here. The block covers a region that is normally 30 to 40 map units long. A locus (r(Sk-2)) conferring resistance to Sk-2 K maps to the left end of the recombination block. Recombination is normal in r(Sk-2) × Sk sensitive but blocked in Sk-2 K × r(Sk-2); so the block does not depend upon killing. By selective plating, Sk K stocks carrying genetic markers within the block were obtained at frequencies on the order of 10 −5 or 10 −6 . Since this tight block is far beyond what has been observed for genetic reduction of recombination, a structural basis is assumed. No evidence of chromosome rearrangement was obtained. Crosses homozygous for Sk-2 K show normal crossing-over and map order for the flanking markers cum and his-7 and three included markers (acr-7, acr-2, and leu-1). Results would be consistent with a divergence of sequence great enough to interfere with homologous pairing. Key words: meiotic drive, Neurospora, crossover suppressor.