de la Chapelle A, Tippett P A, Wetterstrand G, Page D
Nature. 1984;307(5947):170-1. doi: 10.1038/307170a0.
Of the hypotheses put forward to explain why occasional individuals with two X chromosomes are nonetheless male, the one that has attracted most attention is the possibility that one of the X chromosomes has obtained a small piece of Y chromosome which is sufficient to produce 'maleness'. This hypothesis was based primarily on the observation that in two families with XX males both fathers were Xg(a+) and both probands Xg(a-). (Xg shows X-linked dominant inheritance.) This theory holds that an anomalous X-Y interchange at meiosis in the father resulted in the paternal X chromosome's losing the Xg gene and acquiring a male-determining gene from the Y chromosome. While, for example, the frequencies of Xg phenotypes among XX males and the cytogenetic observation of a structural abnormality in one X are compatible with this hypothesis, direct evidence of it is lacking. Here we describe an XX male who expresses his father's allele for 12E7, a Y-linked marker, but fails to express his father's allele for Xg, an X-linked marker. These findings strongly suggest that anomalous X-Y interchange occurred in this case and perhaps in that of many other XX males. We suggest that a male-determining gene on the Y has also been translocated to the X and caused maleness in the proband. These results are discussed in the light of current models of X-Y chromosomal homology.
在为解释为何偶尔会出现拥有两条X染色体的个体却是男性而提出的诸多假说中，最受关注的是这样一种可能性：其中一条X染色体获得了一小段Y染色体，而这足以导致“男性化”。这一假说主要基于以下观察结果：在两个XX男性的家族中，父亲均为Xg(a+)，而先证者均为Xg(a-)。（Xg表现为X连锁显性遗传。）该理论认为，父亲减数分裂时发生的异常X-Y互换导致父源X染色体丢失了Xg基因，并从Y染色体获得了一个男性决定基因。例如，XX男性中Xg表型的频率以及在一条X染色体上观察到的结构异常的细胞遗传学证据与这一假说相符，但仍缺乏直接证据。在此我们描述了一名XX男性，他表达了父亲的Y连锁标记12E7的等位基因，但未表达父亲的X连锁标记Xg的等位基因。这些发现有力地表明，在该病例以及许多其他XX男性病例中都发生了异常的X-Y互换。我们认为，Y染色体上的一个男性决定基因也已易位至X染色体，并导致了先证者的男性化。我们根据当前的X-Y染色体同源性模型对这些结果进行了讨论。
