Desynaptic is a meiotic mutant first reported by Nelson and Clary (J. Hered. 43:205-210, 1952). Cytogenetical analysis shows dy mutants do not display orderly disjunction during anaphase I, after crossing-over has occurred (Maguire, Chromosoma 65:173-183, 1978). Mutant plants can be phenotyped easily by a reduced proportion (65-75%) of normal pollen and this can be verified with pachytene analysis. Cytogenetic analysis of asynaptic, another maize meiotic mutant, did not corroborate marker-based approaches to recovering meiotic products so we tested the hypothesis that dy is a gene which modifies recombination frequencies.
Mutant dy plants from stock verified by Maguire et al. (Genome 34:879-887, 1991) were crossed to a chromosome 1L rare-allele stock and a single F1 parent was selfed to produced 200 F2 plants segregating for dy. Mutant and wild-type F2 parents which were segregating for marker loci were then selfed to produced F3 offspring. Linkage distances were compared between a mutant dy/dy F2 family and a wild-type Dy/dy F2 family composed of 100 offspring each.
Preliminary data show that the wild-type offspring had a total map distance comparable to our previous study (72.3 cM for the amp1-gdh1 interval on chromosome 1L) but the dy/dy mutant offspring showed a total of 46.9 cM for the same interval.
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