FGSC #7386

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Reporting Genes: Sk-2 acr-2

Species: crassa

Allele: P KH5

Alternate Strain Number: 3272

Depositor: BCT

Linkage Group: III III

Mating Type: a

Species Number: 10

Opposite Mating Type: 7385

Deposit Sheet ↗

Genes

Locus	Cultural Requirements	Link Group	Type
acr-2	III. Linked to thi-4 (0/286). Left of sc (3 to 6%) and spg (1 to 11%) (498, 816). acr-2 has been shown left of the centromere on published maps but without direct evidence. acr-2and trp-1 (on IIIR) cosegregated at the second division in 1 of 13 asci (H.B. Howe, Jr., personal communication), which would favor a right arm location. Resistant to acriflavine (494, 495); also resistant to 3-amino-1,2,4-triazole (seven alleles tested) (494). Resistance is probably dominant (heterokaryon tests) (498). Not resistant to malachite green. An excellent stable marker, fully fertile, with unambiguous scoring. Sizable inocula should be used to avoid false-negative tests. Use acriflavine at 50 µg /ml in minimal agar medium (816) (higher concentrations may be used) and aminotriazole at 0.5 mg/ml; both added before autoclaving.	III	B
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