An X-Y homologous pairing segment in tree shrews (Tupaia).
High-resolution early replication banding of tupaia metaphase chromosomes revealed a synchronous early replicating segment in the short-arm telomeric regions of the active and inactive X chromosomes and in the long-arm telomeric region of the Y chromosome. Hybridization with the human-derived pseudoautosomal probe 113F (STIR) showed that this repeat is conserved and specifically localized within these synchronously early replicating segments of the X short arm and the Y long arm of all three tupaia species (Tupaia belangeri, T. chinensis, and T. glis) investigated. Moreover, meiotic studies demonstrated that a synaptonemal complex is formed at one telomeric end of the XY bivalent during the pachytene stage of meiosis in a male T. glis specimen. Thus, apart from the mouse, the tupaias are the first nonprimate mammals for which cytogenetic and molecular evidence is provided that their highly heteromorphic X and Y chromosomes share a conserved homologous segment in the telomeric position, a location that is compatible with pairing and crossing-over in male meiosis. Taken together, these observations strongly, albeit indirectly, suggest that this chromosome segment at the tip of a sex-chromosome arm might behave pseudoautosomally.
Toder
R
R
Institut für Humangenetik und Anthropologie, Universität Freiburg, FRG.
Rumpler
Y
Y
von Holst
D
D
Schempp
W
W
D000818:Animals; D015139:Blotting, Southern; D002478:Cells, Cultured; D017124:Conserved Sequence; D004247:DNA; D004261:DNA Replication; D005260:Female; D006801:Humans; D017403:In Situ Hybridization; D008297:Male; D008540:Meiosis; D012091:Repetitive Sequences, Nucleic Acid; D014417:Tupaia / Q000235:genetics*; D014960:X Chromosome; D014998:Y Chromosome
D004247:DNA