Pack S D, Borodin P M, Serov O L, Searle J B
Institute of Cytology and Genetics, Russian Academy of Sciences, Novosibirsk.
Chromosoma. 1993 May;102(5):355-60. doi: 10.1007/BF00661279.
Common shrews have an XX/XY1Y2 sex chromosome system, with the "X" chromosome being a translocation (tandem fusion) between the "original" X and an autosome; in males this autosome is represented by the Y2 chromosome. From G-banded chromosomes, the Y2 is homologous to the long arm and centromeric part of the short arm of the X. The region of the X that is homologous to the Y2 and also the telomeric region of the short arm of the X were found to be early replicating in somatic cells from a female shrew after 5-bromo-2'-deoxyuridine (BrdU) treatment in vitro. The remainder of the short arm of the X was shown to be late replicating. Electron microscopic examination of synaptonemal complexes in males at pachytene revealed pairing of the Y2 axis with the long arm of the X, and Y1 with the short arm. At early stages of pachytene, there is apparently extensive nonhomologous pairing between the X and Y1. In essence, the short arm of the shrew X chromosome behaves like a typical eutherian X chromosome (it is inactivated in female somatic cells and is paried with the Y1 during male meiosis) while the long arm behaves like an autosome (escapes the inactivation and pairs with the Y2).
普通鼩鼱具有XX/XY1Y2性染色体系统，其中“X”染色体是“原始”X染色体与一条常染色体之间的易位（串联融合）；在雄性中，这条常染色体由Y2染色体代表。从G带染色体来看，Y2与X染色体短臂的长臂和着丝粒部分同源。在体外经5-溴-2'-脱氧尿苷（BrdU）处理的雌性鼩鼱体细胞中，发现与Y2同源的X染色体区域以及X染色体短臂的端粒区域是早期复制的。X染色体短臂的其余部分显示为晚期复制。对雄性粗线期联会复合体的电子显微镜检查揭示，Y2轴与X染色体长臂配对，Y1与短臂配对。在粗线期早期，X与Y1之间显然存在广泛的非同源配对。从本质上讲，鼩鼱X染色体的短臂表现得像典型的真兽类X染色体（在雌性体细胞中失活，在雄性减数分裂期间与Y1配对），而长臂表现得像常染色体（逃避失活并与Y2配对）。
