Worm Breeder's Gazette 7(1): 84
These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.
Why don't chromosomes at meiotic prophase fall apart (or undergo disjunction) when they are supposed to? Part of the answer lies in peculiar knobs attached to the synaptonemal complexes (SC) in C. elegans hermaphrodites and males. It has recently been reported that these 'SC knobs' may represent active regions of DNA, as opposed to the more compact chromatin usually found at pachytene (Goldstein and Slatan, 1981). Also, the number and distribution of these SCKs vary, such that the wild-type hermaphrodite has 6 SCKs (and shows 0.01% nondisjunction) while the him8 mutant (with 37% nondisjunction) has no such knobs (Goldstein, 1981). The him4 mutant, which shows 16% nondisjunction and represents an intermediate situation, has 3 SCKs. Thus, it was suggested that the presence or absence of SCKs may mediate the nondisjunction process, such that the product of the active DNA region inhibits nondisjunction if present (6 SCKs in wild- type-0.01%) and if this product is not present, then nondisjunction occurs (no SCKs in him8, 37% nondisjunction). Recently, further evidence has been obtained to support this theory. There are two SCKs in wild-type young males (4 days) this represents a true sex- difference) however, in older males (7-9 days) no such SCKs are present. The report by Rose and Baillie (1979) that nondisjunction increases with age (as revealed by increase in male progeny) correlates with the absence of SCKs in older males.