Nature and organization of the sequence variations in the long-range periodicity calf satellite DNA I.

The nucleotide sequences of a series of cloned repeats of the bovine satellite DNA I have been established and compared to the average sequence already determined by the other workers. Variations, which are essentially single base changes, deletions or additions, are found within clustered copies and, thus, define subfractions and domains of the satellite DNA. These results are confirmed by restriction enzyme analysis of the cloned repeats or of the total purified satellite DNA. These subfractions are essentially overlapping. Certain short regions of the DNA repeat do not appear to be involved in the changes, which are spread in a concerted way through the whole bovine karyotype. The significance of these results is discussed in the light of the recent suggestion made that gene conversion-like events are susceptible to introduce homogeneity of polymorphism within the elements of repeated families of DNA sequences.