人类染色体的多态性与主体异染色质有关。第9号染色体异染色质区的大小和位置的改变在人群中出现的频率很高,特别引人瞩目。迄今为止,已有大量的文献报道了9号染色体的这种多态现象。最近,我们在三例无血缘关系的家庭中发现了9号染色体一种新的变异:在增长的次缢痕异染色质区内,出现一条明显的深带。现将已做家系调查的两例报道于下。例1.王××(遗883号),男,18岁,因肌肉萎缩于1981年11月来遗传门诊。外周血淋巴细胞染色体 G 显带检查发现一条9号染色体 qh 增长,其中部有一条明显的深染带,其它染色体未发现异常。追查其家系,发 Human chromosome polymorphism and the main heterochromatin. The size and location of heterochromatic regions on chromosome 9 are particularly prevalent in the population. So far, a large number of literatures have reported this polymorphism of chromosome 9. Recently, we found a new mutation in chromosome 9 in three unrelated families: a clear deep band appeared in the growing heterochromatin region of the second lesion. Two cases of family history surveys are now reported below. Example 1. Wang × × (left 883), male, 18 years old, due to muscle atrophy in November 1981 to the genetic clinic. Peripheral blood lymphocyte chromosome G banding examination revealed a chromosome 9 qh growth, in which there is a clear deep band, the other chromosomes found no abnormalities. Tracing its family, hair