Sex-chromosome pairing through heterochromatin in the African rodent Lemniscomys barbarus (Rodentia, Muridae). A synaptonemal complex study.
Giemsa-stained spread preparations and microspread preparations of Lemniscomys barbarus spermatocytes were made to investigate the meiotic behaviour of the peculiar sex chromosomes of this species. A typical sex vesicle is absent, as the X and Y chromosomes appear unfolded at zygotene and pachytene. In most cells, the sex chromosomes are associated at distal segments at metaphase I, probably as a consequence of a distal chiasma. The pairing segment is located in the heterochromatic regions of both sex chromosomes, which include silent ribosomal cistrons interspersed throughout the heterochromatin. This may suggest a possible involvement of ribosomal genes in both pairing and recombination processes. X-Y pairing proceeds beyond the pseudoautosomal region, thus involving heterologous segments of the differential regions, a fact that is clearly evident at the Y centromeric region.
Departamento de Genética, Facaltad de Ciencias, Universidad de Granada, Spain.
S
S
Stitou
R
R
Jiménez
R
R
Díaz de La Guardia
M
M
Burgos
D000818:Animals; D006570:Heterochromatin / Q000235:genetics*; D008297:Male; D008540:Meiosis; D051379:Mice; D011995:Recombination, Genetic; D012730:Sex Chromosomes; D013090:Spermatocytes / Q000648:ultrastructure; D014960:X Chromosome / Q000648:ultrastructure; D014998:Y Chromosome / Q000648:ultrastructure
D006570:Heterochromatin