Worm Breeder's Gazette 8(2): 18
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.
Nuclear morphology at the pachytene stage of meiosis is altered in the rad-4 mutant such that the nuclei are 50% of the volume as that of wildtype. In addition, the X:A ratio differs in rad-4 as compared with the wild-type. Six synaptonemal complexes (SC), consisting of two lateral elements and a central element, are present in the pachytene nuclei of the C. elegans hermaphrodites. The XX bivalent pairs synchronously with the autosomes. Three specific chromosomes can be identified out of the total of six: 1) The XX bivalent, SC#1, is the shortest; 2) the longest bivalent, SC#6, carries the nucleolar organizer region at the extreme end; and 3) the SC#5 has two 'Disjunction Regulator Regions' (DRR) located approximately one m apart from each other. These DRRs either promote disjunction or inhibit nondisjunction of the X chromosome. The decrease in the rate of X chromosome nondisjunction in this mutant is not related to the structure of the SC, but may be related to the number of DRRs, specifically it is observed in the rad-4 mutant that the DRRs occur with a higher frequency than in wild-type. Other SC associated structures, such as recombination nodules, have not been observed in this strain or any other strain of C. elegans.