THE COMPLETE MITOCHONDRIAL-DNA SEQUENCE OF THE HORSE, EQUUS-CABALLUS - EXTENSIVE HETEROPLASMY OF THE CONTROL REGION

The sequence of the mitochondrial (mt) DNA of the horse (Equus caballu s) was determined. The length of the sequence presented is 16 660 bp. This figure, however, is not absolute due to pronounced heteroplasmy c aused by variable numbers of the motif GTGCACCT in the control region of different molecules. Boundaries of the 13 peptide-coding genes were determined by the presence of start and stop codons, and by analogy w ith other eutherian mtDNAs. Three genes (COIII, NADH3 and NADH4) were not terminated by a stop codon. Comparison among the peptide-coding ge nes of the horse and eight other mammals suggests that the boundaries of some mt genes should be redefined. The number of repeats in the con trol region was determined by sequencing 77 different clones (20 direc t plus 57 PCR clones). The number of repeats ranged from 2 to 29. Ther e was a pronounced overrepresentation of clones with many repeats (22- 27). Very few clones had a repeat number that was close to the mean nu mber of repeats.