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：1971
卷号：68
期号：12
页码：3175-3179
DOI：10.1073/pnas.68.12.3175
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：DNA containing the multiple genes for 5S RNA has been isolated from the genome of Xenopus laevis. Whereas 5S RNA is about 57% G + C, the 5S DNA has a base composition of about 33-35% GC and consists of two alternating regions that differ in base composition by at least 20% GC. A denaturation map of 5S DNA analyzed by electron microscopy demonstrates that the repeating pattern is regular and each repeating unit has a mass of about 500,000 daltons. If one gene for 5S RNA (84,000 daltons native) were present in each repeat, it should comprise about 16.8% of 5S DNA. This arrangement is confirmed, since 6.8% of pure 5S DNA (13.6% of its base pairs) hybridized with 5S RNA. The remaining 83% of each repeating unit is considered to be "spacer" DNA. The 5S RNA hybridizes with about 0.05% of the bulk DNA of X. laevis, so that 5S DNA comprises about 0.7% of the total nuclear DNA. This is equivalent to about 24,000 repeating units for each haploid complement of DNA. These repeats are highly clustered; as many as 86 have been visualized along a single DNA molecule.
关键词：gene isolation ; 5S RNA ; repetitive DNA ; spacer DNA
