EVOLUTION AND RECOMBINATION OF BOVINE DNA REPEATS

The history of the abundant repeat elements in the bovine genome has b een studied by comparative hybridization and PCR. The Bov-A and Bov-B SINE elements both emerged just after the divergence of the Camelidae and the true ruminants. A 31-bp subrepeat motif in satellites of the B ovidae species cattle, sheep, and goat is also present in Cervidae (de er) and apparently predates the Bovidae. However, the other components of the bovine satellites were amplified after the divergence of the c attle and the Caprinae (sheep and goat). A 23-bp motif, which as subre peat of two major satellites occupies 5% of the cattle genome, emerged only after the split of the water buffalo and other cattle species. D uring the evolution of the Bovidae the satellite repeat units were sha ped by recombination events involving subrepeats, other satellite comp onents, and SINE elements. Differences in restriction sites of homolog ous satellites indicate a continuing rapid horizontal spread of new se quence variants.