Phelan M C, Morton C C, Stevenson R E, Tanzi R E, Stewart G D, Watkins P C, Gusella J F, Amos J A
Greenwood Genetic Center, NC.
Am J Hum Genet. 1988 Oct;43(4):511-9.
Genomic single-copy DNA fragments were used to characterize an undetected chromosome translocation in an individual whose metaphase chromosome analysis revealed apparent monosomy 21. Eight RFLPs detected by six probes were used to identify homologous sequences from chromosome 21 in DNA digests from the proband and her parents. These family studies showed that the proband was disomic for the distal region of 21q. Reverse banding and in situ hybridization of chromosome 21-specific probes to metaphase chromosomes from the proband revealed a de novo translocation with breakpoints at 5p13 or 14 and 21q11 or 21. In situ hybridization permitted orientation of the translocated portion of chromosome 21 on the derivative chromosome 5 and, in conjunction with molecular analysis and previous mapping studies, refined the physical map for the long arm of chromosome 21.
基因组单拷贝DNA片段被用于鉴定一名个体中未被检测到的染色体易位，该个体的中期染色体分析显示明显的21号染色体单体。六个探针检测到的八个限制性片段长度多态性（RFLP）被用于从先证者及其父母的DNA消化物中鉴定来自21号染色体的同源序列。这些家系研究表明，先证者在21q的远端区域是二体的。对先证者中期染色体进行21号染色体特异性探针的反向显带和原位杂交，揭示了一个新发易位，断点位于5p13或14以及21q11或21。原位杂交确定了21号染色体易位部分在衍生5号染色体上的方向，并结合分子分析和先前的定位研究，完善了21号染色体长臂的物理图谱。
