FGSC #3115

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Reporting Genes: Sk-2 (Sk from N. intermedia)

Species: crassa

Allele: P7133

Alternate Strain Number: 3133

Depositor: DDP

Linkage Group: IIIC

Mating Type: a

Species Number: 10

Opposite Mating Type: 3114

Deposit Sheet ↗

Genes

Locus	Cultural Requirements	Link Group	Type
Sk-2	III. Second-division segregation rare or absent. The killer allele Sk-2K recombines with his-7 (25%) but suppresses crossing over in the interval r(Sk-2)-1 to leu-1 (29% in controls). (1092). Sk-2K does not recombine with acr-7 (0/1800) or acr-2 (0/100,000) (B.C. Turner, personal communication). Kills ascospores of sensitive genotype after meiosis in crosses heterozygous for the killer allele Sk-2K. In Sk-2K x Sk-2S crosses (Killer x Sensitive), each ascus contains four inviable clear ascospores and four viable black ascospores that are SkK. Ascospores are not killed in SkK x SkK crosses (1092). Meiosis and postmeiotic mitosis appear normal by light microscopy. Sensitive spores first appear abnormal after one nuclear division in the ascospore. Sk-2S nuclei survive if included in the same ascospore with Sk-2(857). Originated in N. intermedia; introgressed into N. crassa. Most strains from nature are sensitive, but resistant strains of N. intermedia are common in some geographic areas, and two resistant strains of N. crassahave been found [see r(Sk-2)-1]. Strains resistant to Sk-2K are not necessarily resistant to Sk-3K. In Sk-2K x Sk-3K crosses, less than 1% of the ascospores are normal and viable (1092; B.C. Turner, personal communication). If Sk-2K and Sk-3K nuclei are included in the same ascospore, both nuclei survive and the spore is not killed (N.B. Raju, personal communication).	III	B