Nucleotide Sequence Variation in Mitochondrial Deoxyribonucleic Acid from Bovine Liver

Abstract

Mitochondrial deoxyribonucleic acid isolated from the liver of pedigreed cows was examined by restriction enzyme analysis. Differences in restriction enzyme patterns of deoxyribonucleic acid from different maternal lineages were observed. These nucleotide sequence differences were scattered over the mitochondrial genome, with some clustering near the origin of deoxyribonucleic acid replication. Most of them appeared to result from the simple loss or gain of a restriction enzyme site and did not appear to involve gross rearrangements of the mitochondrial genome.Within one maternal lineage was a nucleotide sequence variation resulting in the loss of a Hae III restriction enzyme site mapping at 37.1 map units on the bovine mitochondrial genome. This polymorphism segregated among members of the lineage in a manner not easily understood by a simple mutagenic event. Amplification and segregation of mitochondrial deoxyribonucleic acid during maternal transmission to progeny most directly explains this extremely rapid variation in nucleotide sequence within a single maternal lineage.These observations document the existence of a mitochondrial deoxyribonucleic acid polymorphism between and within Holstein cow lineages and should help in understanding molecular genetics of the dairy cow. They additionally demonstrate the utility of patterns of mitochondrial deoxyribonucleic acid restriction enzyme digestion in analyzing maternal lineages of dairy cows.