Finucane B M, Jaeger E, Dunn E, Scott C I
Medical Department of Elwyn, Inc., PA 19063.
Am J Med Genet. 1992 Jan 15;42(2):184-6. doi: 10.1002/ajmg.1320420210.
Various theories have been postulated to account for the unusual inheritance pattern observed in the fragile X syndrome. The recent finding of a secondary amplification of the fragile X mutation in the offspring of carrier females [Oberle et al., 1991; Yu et al., 1991] is consistent with a maternal imprinting process. Laird [1987] has proposed that the fragile X mutation blocks complete reactivation of a previously inactivated fragile X chromosome. We have tested whether or not such a localized block extends as far distal as the red/green color-vision complex at Xq28. We found no evidence of color-vision defects among 25 male subjects with the fragile X syndrome. A fragile X positive woman also had normal color vision, despite being an obligate carrier of her father's gene for red/green color blindness. We conclude that the fragile X gene does not affect the function of neighboring color-vision genes, nor does it affect their ability to compensate adequately for inherited color deficiency on the homologous X chromosome in females.
人们提出了各种理论来解释脆性X综合征中观察到的异常遗传模式。最近在携带者女性的后代中发现脆性X突变的二次扩增[奥伯勒等人，1991年；于等人，1991年]，这与母系印记过程一致。莱尔德[1987年]提出，脆性X突变会阻止先前失活的脆性X染色体完全重新激活。我们已经测试了这种局部阻断是否一直延伸到Xq28的红/绿颜色视觉复合体的远端。我们在25名患有脆性X综合征的男性受试者中没有发现色觉缺陷的证据。一名脆性X阳性女性也有正常的色觉，尽管她是父亲红/绿色盲基因的必然携带者。我们得出结论，脆性X基因既不影响相邻色觉基因的功能，也不影响它们在女性同源X染色体上充分补偿遗传色觉缺陷的能力。
