A LOW-RATE OF REPLACEMENT SUBSTITUTIONS IN 2 MAJOR OVIS-ARIES MITOCHONDRIAL GENOMES

Two mitochondrial DNA molecules which represent major Ovis aries mtDNA haplogroups were cloned and comparatively sequenced to assess the deg ree of intraspecific variation. A total of 9623 bp that correspond to 58% of both mitochondrial genomes were determined. The control region, the Cytb, ND2, ND3, ND4L, COIII and 12 tRNA genes, including the orig in of L-strand replication, were completely characterized. Partial seq uence information was obtained from the 12S and 16S rRNA and an additi onal six protein coding and six tRNA genes. The control regions of the two mtDNAs showed a nucleotide divergence of 4.34% while coding regio ns differed by 0.44%. The number of sheep coding region substitutions was similar to values observed in intraspecific comparisons of mitocho ndrial DNAs that represent remote points in genealogical trees of mice and humans. However, replacement substitutions were only observed at similar to 30% of the rate in mice and similar to 20% of the rate in h umans. Nucleotide substitutions with a potential for phenotypic effect s were found in the 12S aod 16S rRNA and in the ND1 and COIII genes.