Howell R T, Roberts S H, Beard R J
J Med Genet. 1976 Dec;13(6):496-500. doi: 10.1136/jmg.13.6.496.
Four cases of Turner's syndrome are presented in which an apparent X isochromosome i(Xq) has been found to possess two regions of centromeric heterochromatin. It is suggested that these chromosomes were isodicentric structures capable of functioning as monocentric elements as a result of the inactivation of one centromere. The prevalence of mosaicism is believed to be a consequence of the dicentric nature of these chromosomes, and it is considered possible that a high proportion of X isochromosmes are structurally dicentric. Banding patterns showed that the exchange site involved in the formation of the dicentric chromosome was different in at least three of the cases.
本文报告了4例特纳综合征病例，其中发现一条明显的X等臂染色体i(Xq)具有两个着丝粒异染色质区域。有人提出，这些染色体是等双着丝粒结构，由于一个着丝粒失活，能够作为单着丝粒元件发挥作用。嵌合体的普遍存在被认为是这些染色体双着丝粒性质的结果，并且认为很大比例的X等臂染色体在结构上是双着丝粒的。染色体带型显示，至少在3例病例中，参与双着丝粒染色体形成的交换位点是不同的。
