Renaturation rate studies of a single family of interspersed repeated sequences in human deoxyribonucleic acid.

We have investigated the renaturation kinetics of a single family of cloned interspersed repeated sequences isolated from human DNA. Cross-renaturation studies of individual cloned sequences reveal heterogeneity in both the renaturation rate and the thermal stability of heteroduplexes formed from members of this family of sequences. However, cloned members of this family all renature with approximately the same number of copies in the human genome, demonstrating that they are a single family of sequences by the criterion of DNA renaturation kinetics. When a single cloned member of the family is renatured with total human DNA as a function of temperature, the thermal stability of the renatured heteroduplexes is found to be independent of the renaturation temperature over the range 25 degrees C below to 4 degrees C above the melting temperature. Further, the number of genomic copies with which this cloned family member reacts is also independent of the renaturation temperature from 25 degrees C below up to the melting temperatures. These observations demonstrate a remarkable degree of homogeneity in the evolutionary sequence divergence of members of this family. These results also demonstrate that renaturation kinetics can accurately measure the number of genomic copies of interspersed repeated DNA sequences.