期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1977
卷号：74
期号：11
页码：4932-4936
DOI：10.1073/pnas.74.11.4932
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：A cloned 14.3-kbase segment of Drosophila melanogaster rDNA (Dm207) is described in which only a 4-kbase region is homologous to a cloned 17-kbase rDNA repeating unit, Dm103; this 4-kbase region consists of part of the 28S rRNA gene and most but not all of the adjacent transcribed spacer that normally connects the 18S and 28S genes. The transcribed spacer in Dm207 is interrupted by a 2.2-kbase stretch of DNA that does not contain any 18S gene sequences. At the other end of the 4-kbase homology, the 28S gene is interrupted by an 8.1-kbase stretch of DNA at a position equivalent to the site of the 28S insertion found in the 17-kbase units. The question of whether the 2.2-kbase and 8.1-kbase interrupter segments in Dm207 derive from longer insertions into the transcribed spacer and 28S genes of a very long repeating unit (greater than or equal to 22 kbases) or represent a region of the chromosomal DNA into which a 4-kbase fragment of rDNA has been inserted is discussed.
