Endow S A
Cell. 1980 Nov;22(1 Pt 1):149-55. doi: 10.1016/0092-8674(80)90163-4.
Recent studies indicate that genes from only one nucleolus organizer undergo replication during polytenization of salivary gland cells of X/Y flies. This report presents evidence that this is also true X/X polytene cells. Interstrain hybrids were constructed which contain X chromosomes with different rDNA hybridization patterns following digestion with Eco RI, and DNA from diploid or polytene tissue was analyzed using Southern transfers. DNA from diploid tissue of X/X hybrids shows rDNA patterns from both X chromosomes, while DNA from polytene tissue of hybrids shows a pattern characteristic of only one of the X chromosomes. The polytene pattern of the hybrid is independent of whether the dominant X chromosome was derived from the female or male parent. These results suggest that genes from only one nucleolus organizer undergo multiple rounds of replication in X/X polytene cells, and account for the finding that X/O and X/X polytene cells contain similar levels of rDNA without postulating compensation as a ribosomal gene rectification mechanism.
最近的研究表明，在X/Y果蝇唾液腺细胞多线化过程中，只有一个核仁组织区的基因会进行复制。本报告提供的证据表明，这在X/X多线细胞中也是如此。构建了种间杂种，其X染色体在用Eco RI消化后具有不同的rDNA杂交模式，并使用Southern转移分析二倍体或多线组织的DNA。X/X杂种二倍体组织的DNA显示出来自两条X染色体的rDNA模式，而杂种多线组织的DNA显示出仅一条X染色体特有的模式。杂种的多线模式与显性X染色体是来自雌性还是雄性亲本无关。这些结果表明，在X/X多线细胞中，只有一个核仁组织区的基因会进行多轮复制，这也解释了为什么X/O和X/X多线细胞含有相似水平的rDNA，而无需假设补偿作为核糖体基因校正机制。
