FGSC #2920

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Reporting Genes: mei-1

Species: crassa

Allele: no#

Alternate Strain Number: 4182: = Smit

Mutagen: M

Depositor: DDP

Linkage Group: IVR

Mating Type: a

Species Number: 10

Genetic Background: M

Opposite Mating Type: 2919

Deposit Sheet ↗

Genes

Locus	Cultural Requirements	Link Group	Type
mei-1	IVR. Linked to arg-2 (<1%), probably to the right (995). Meiosis is impaired in homozygous crosses. Recessive. Meiotic divisions occur and many ascospores are produced, but 70 to 90% are inviable and white. The viable ascospores are usually disomic for one or more linkage groups, indicating high nondisjunction at the first division (254, 995). Chromosome pairing is defective: axial elements of synaptonemal complex are present, but a completed complex is rarely seen. Separation at anaphases I and II is defective, leading to four-poled second and third division spindles (625). Not sensitive to UV, methyl methane sulfonate, ionizing radiation (939), or histidine (939; D. Newmeyer, unpublished data). mei-1 is present in wild-collected strain Abbott 4A (995), which is an ancestor of many Beadle and Tatum mutants (68). Possible allele asc(DL243)complements mei-1 but did not recombine with it (0/3,000) (253). DL243 and mei-1 strains differ phenotypically. In DL243 mutants, the major block is before karyogamy; the few asci produced have normal meiosis I but high nondisjunction at meiosis II, with most chromosomes usually attached to only one spindle-pole body (254). Possible allele asc(DL95) complements mei-1 and asc(DL243), but did not recombine with DL243 (0/96) (253). DL95 is phenotypically like mei-1 but is less extreme (254).	IVR	B