Israel M H
Am J Med Genet. 1987 Jan;26(1):19-31. doi: 10.1002/ajmg.1320260106.
We suggest the existence of an autosomal suppressor gene, S, which is fairly common in the general population and acts to inhibit expression of the fra(X) gene, F. The suppression is effective in males who are hemizygous for F only if they are homozygous for S, while it is effective in females who are heterozygous for F if they are at least heterozygous for S. Thus, the fra(X) phenotype is not expressed in genotypes F-SS,FfSS, FfSs, while it is expressed in genotypes F-Ss, F-ss, Ffss. With a frequency of SS in the general population of approximately 20%, this hypothesis can explain the observed penetrance of about 80% in F- males and about 30% in Ff females. It can also explain the very low frequency of fra(X) expression in Ff females who are daughters or mothers of non-penetrant F- males, and a lower penetrance in siblings of non-penetrant F- males than in grandsons of these males. The model is in good quantitative agreement with other unique characteristics of fra(X) inheritance.
我们认为存在一种常染色体抑制基因S，它在普通人群中相当常见，作用是抑制脆性X基因F的表达。只有当男性对于F为半合子且对于S为纯合子时，这种抑制才对他们有效；而对于女性，当她们对于F为杂合子且对于S至少为杂合子时，抑制才有效。因此，脆性X表型在基因型F-SS、FfSS、FfSs中不表达，而在基因型F-Ss、F-ss、Ffss中表达。鉴于普通人群中SS的频率约为20%，这一假设可以解释在F-男性中观察到的约80%的外显率以及在Ff女性中约30%的外显率。它还可以解释在非外显F-男性的女儿或母亲这类Ff女性中脆性X表达的频率非常低，以及在非外显F-男性的兄弟姐妹中的外显率低于这些男性的孙子辈中的外显率。该模型在数量上与脆性X遗传的其他独特特征高度吻合。
