de Capoa A, Felli M P, Baldini A, Rocchi M, Archidiacono N, Aleixandre C, Miller O J, Miller D A
Dipartimento di Genetica e Biologia Molecolare, Università La Sapienza, Rome, Italy.
Hum Genet. 1988 Aug;79(4):301-4. doi: 10.1007/BF00282165.
The relative number of ribosomal RNA genes of the acrocentric chromosomes in one individual was measured by counting grains after in situ hybridization of 3H-labeled human 18S rDNA to fixed metaphase chromosomes. The relative amount of ribosomal RNA gene activity of each of the same chromosomes was estimated by determining the frequency with which the chromosome's nucleolus organizer region (NOR) was silver stained, the size of the silver-stained region, and how often the chromosome was found in satellite association. Results were similar in phytohemagglutinin-stimulated T-lymphocytes, Epstein-Barr virus transformed lymphoblasts, and fibroblasts. One chromosome 21 had few gene copies and low activity. One chromosome 22 had many gene copies but low activity. Both chromosomes 14 had few gene copies but high activity. The level of expression that can be achieved by rRNA gene clusters can, therefore, be determined by factors other than the number of gene copies.
通过将3H标记的人18S rDNA与固定的中期染色体进行原位杂交后计数银粒，来测量一个个体中近端着丝粒染色体的核糖体RNA基因的相对数量。通过确定染色体核仁组织区（NOR）被银染的频率、银染区域的大小以及该染色体在随体联合中出现的频率，来估计相同染色体中每条染色体的核糖体RNA基因活性的相对量。在植物血凝素刺激的T淋巴细胞、爱泼斯坦-巴尔病毒转化的淋巴母细胞和成纤维细胞中结果相似。一条21号染色体的基因拷贝数少且活性低。一条22号染色体的基因拷贝数多但活性低。两条14号染色体的基因拷贝数少但活性高。因此，rRNA基因簇能够达到的表达水平可由基因拷贝数以外的因素决定。
