Nucleic Acids Research, 1977, Vol. 4, No. 5 1553-1568
© 1977
Articles |
Exploration of long and short repetitive sequence relationships in the sea urchin genome
Division of Biology, California Institute of Technology Pasadena, CA 91125, USA
Received January 29, 1977.
Long and short repetitive sequences of sea urchin DNA were prepared by reassoci-ation of 2000 nucleotide long fragments to Cot 4 and digestion with the single strand specific nuclease S1. The S1 resistant duplexes were separated into long repetitive and short repetitive fractions on Agarose A50. The extent of shared sequences was studied by reassociating a labeled preparation of short repetitive DNA with an excess of unlabeled long repetitive DNA. Less than 10% of the long repetitive DNA preparation was able to reassociate with the short repetitive DNA. Thus the long and short repetitive elements appear to be principally independent sequence classes in sea urchin DNA.
Precisely reassociating repetitive DNA was prepared by four successive steps of reassociation and thermal chromatography on hydroxyapatite. This fraction (3% of the genome) was reassociated by itself or with a great excess of total sea urchin DNA. The thermal stability of the products was identical in both cases (Tm=81°C), indicating that precisely repeated sequences do not have many imprecise copies in sea urchin DNA.
1Present address: National Cancer Institute, NIH, Bethesda, Md. 20014
2Present address: Department of Biology, Purdue University, Lafayette, Indiana 47907
3Also Staff Member, Carnegie Institution of Washington, Washington, D.C.20005