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.

Chromosomes in C. elegans

P. Goldstein

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.