Toder R, Rumpler Y, von Holst D, Schempp W
Institut für Humangenetik und Anthropologie, Universität Freiburg, FRG.
Cytogenet Cell Genet. 1993;63(2):135-40. doi: 10.1159/000133519.
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.
树鼩中期染色体的高分辨率早期复制带显示，在活性和非活性X染色体的短臂端粒区域以及Y染色体的长臂端粒区域存在同步早期复制片段。与人源假常染色体探针113F（STIR）杂交表明，这种重复序列是保守的，并且特异性地定位在所有三种被研究的树鼩物种（北树鼩、中缅树鼩和笔尾树鼩）的X短臂和Y长臂的这些同步早期复制片段内。此外，减数分裂研究表明，在雄性笔尾树鼩标本减数分裂粗线期，XY二价体的一个端粒末端形成了联会复合体。因此，除了小鼠之外，树鼩是首个有细胞遗传学和分子证据表明其高度异型的X和Y染色体在端粒位置共享保守同源片段的非灵长类哺乳动物，该位置与雄性减数分裂中的配对和交叉相容。综上所述，这些观察结果强烈地（尽管是间接的）表明，性染色体臂末端的这个染色体片段可能表现出假常染色体的行为。
