Worm Breeder's Gazette 7(2): 37
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.
Only five synaptonemal complexes (SC) (representing the 5 autosomes) are present in wild type him-4 and him-8, ditis hereas there are six SCs (accounting for 5 autosomal bivalents and the XX bivalent) in the C. elegans hermaphrodite. The equivalent X chromosome of the male is present as a heterochromatic 'X-body' in spermatocyte pachytene nuclei. The XX bivalent in wild-type, him-4 and him-8 hermaphrodites (SC#l, 2.5 m in length) represented 6% of the total karyotype length and a SC of this size is missing from the respective male karyotypes. This corresponds with the fact that the total male karyotype length is only approximately 94% that of the hermaphrodite. Associated with the central element of the SC are structures termed 'SC Knobs' that were first described in the wild type hermaphrodite (Goldstein and Slaton, 1982). The six SC knobs present in the wild-type hermaphrodite oocyte pachytene nuclei and the two SC knobs in the male spermatocyte pachytene nuclei are apparently randomly placed with the exception that they are never found at the ends of the SC. This is also true in him-4 and him-8 in which case there are 3 and zero SC knobs in the hermaphrodites, respectively, and one SC knob each in the male pachytene nuclei. The decrease in number of SC knobs in hermaphrodite to male represents a true sex difference. The presence or absence of the SC knobs may influence the X chromosome nondisjunction process and this effect is not localized to the region of the SC on which the SC knob is located.