Synaptonemal complex analysis of domestic sheep (Ovis aries) with Robertsonian translocations. III. Deficient pairing and NOR role in Massey III heterozygotes.
Spermatocytes from rams heterozygous for Massey translocation III (t(3)7;25) contained one trivalent and those from the rams heterozygous for both Massey translocations I and III (t1t3) contained two trivalents. Where two trivalents and the XY pair are present in the same nucleus they may form a synaptonemal complex (SC), but no SC segment is found between the two trivalents. The frequency of pairing abnormality in four t3 rams and two t1t3 rams did not significantly differ from that in the normal sheep, but t3 trivalents with diverse abnormal configurations were recorded. A hypothesis was proposed that nucleolar organizer regions (NORs) or nucleoli could account for deficient pairing behaviour and hence chromosome rearrangement, because the NOR region on an NOR-bearing chromosome was usually delayed in pairing, and unpaired regions tended to associate with other unpaired axes or SCs.
Dai
K
K
School of Biological Sciences A-12, University of Sydney, N.S.W., Australia.
Gillies
C B
CB
Dollin
A E
AE
D000818:Animals; D002874:Chromosome Mapping; D006580:Genetic Carrier Screening; D008297:Male; D009697:Nucleolus Organizer Region / Q000648:ultrastructure*; D012756:Sheep / Q000235:genetics*; D013045:Species Specificity; D013090:Spermatocytes / Q000648:ultrastructure*; D013573:Synaptonemal Complex; D014178:Translocation, Genetic; D014960:X Chromosome; D014998:Y Chromosome