Nucleic Acids Research, 1984, Vol. 12, No. 2 973-988
© 1984
MOLECULAR BIOLOGY |
The spread of sequence variants in Rattus satellite DNAs
Section on Genomic Structure and Function, Laboratory of Biochemical Pharmacology, National Institute of Arthritis, Diabetes, and Digestive and Kidney Diseases, National Institutes of Health Building 4, Room 116, Bethesda, MD 20205, USA
Received October 24, 1983. Accepted December 1, 1983.
The genus Rattus has two related families of satellite DNA: Satellite I consists of tandem arrays of a 370 base pair repeat unit which is a dimer of two 185 base pair portions (a, b) which are about 60% homologous. Satellite I' consists of tandem arrays of a 185 base pair repeat unit (a') which is about 85% homologous to a and 60% homologous to b. R. norvegicus contains only satellite I but R. rattus contains both satellites I and I'. We examined certain aspects of satellite DNA evolution by comparing the spacing at which variant repeat units of each satellite have spread among non-variant repeat units in these two species. With but one exception, in R. rattus, 15 different variant repeat units have spread among nonvariant repeat units of satellite I, with a spacing equal to the length of the (a,b) dimer. Similarly, fourteen different variant repeat units of the monomeric satellite I' have mixed among non-variant repeat units with a spacing equal to the length of the (a') monomer. These results suggest that a mechanism involving homologous inter-action among satellite sequences could account for the spread of variant family members. We also found that a sequence variant present in certain portions of the dimeric repeat unit of satellite I is more efficiently amplified (or less efficiently corrected) than variants occurring in other regions. This was not true for the monomeric repeat unit of satellite I'.
1Present address: c/o Dr. David A.Epstein, Department of Industrial Engineering, Israel Institute of Technology, The Technion, Technion City, Haifa, Israel
2Present address: Bio-Rad Laboratories, 2200 Wright Avenue, Richmond, CA 94804, USA