人14p＋标记染色体的分子细胞遗传学研究

一例23岁女性患者因近五、六年来出现胡须、四肢多毛及偶有月经不规则而就诊。细胞遗传学检查发现一个短臂明显增大的亚中着丝粒的14号标记染色体14p ·p 区域GTG显带呈浅染,C-带暗染,都呈均匀的染色区。硝酸银染色在p 远侧端显现一个Ag-NOR,其大小与正常近端着丝粒染色体的无明显差异。应用~3H标记的7.3 kb长的rRNA基因探针进行染色体原位杂交,自显影银颗粒沿整个p 区域分布,p 上的银颗粒数是正常近端着丝粒染色体短臂上银颗粒平均数的5倍。这些结果排除了Y或其他染色体参加的重排形成p 的可能性,并表明Ag-NOR的大小或NOR的数目并不一定与rRNA基因的数量成正比。研究Dp 或Gp 类型的染色体变异,对了解人二倍体细胞内rRNA基因表达的调控有重要意义。

Molecular Cytogenetic Study on the Case with 14p Marker Chromosome

A 23-year-old female was found carrying a submetacentric marker chromosome 14p The short arm of the marker chromosome showed a homogeneously stained region in both G-banded and C-banded preparations and was silver-positive in its distal part in AG-NOR preparation.Using a 3H-labelled 7.3 kb fragment of 18S and 28S rRNA genes as a probe and by chromosomal in situ hybridization,it was demonstrated that the autoradiographic silver grains to be located along entire p part of the marker chromosome.The short arm of the 14p had 5.3 times as many autoradiographic silver grains as that of any other normal aero-centric chromosome,but had no greater NOR activity than did the other acrocentric.The difference of these findings suggested that most of the amplified rRNA genes on the 14p chromosome were inactive,they might be inactivited by a process involving DNA methylation.