Dynamics of mitochondrial DNA evolution in animals: amplification and sequencing with conserved primers.

TLDR

The authors amplified and directly sequenced conserved mtDNA segments from more than 100 animal species using standard primers and PCR on unpurified DNA from nanogram fresh specimens and microgram preserved tissues. Bird and fish mtDNA exhibit the same strong transition bias as mammals, yet birds’ thymine‑deficient light strand reduces T→C changes, and cytochrome b amino‑acid replacements occur faster in mammals and birds—supporting a structural hypothesis—while the primers’ broad taxonomic utility facilitates phylogenetic and population research.

Abstract

With a standard set of primers directed toward conserved regions, we have used the polymerase chain reaction to amplify homologous segments of mtDNA from more than 100 animal species, including mammals, birds, amphibians, fishes, and some invertebrates. Amplification and direct sequencing were possible using unpurified mtDNA from nanogram samples of fresh specimens and microgram amounts of tissues preserved for months in alcohol or decades in the dry state. The bird and fish sequences evolve with the same strong bias toward transitions that holds for mammals. However, because the light strand of birds is deficient in thymine, thymine to cytosine transitions are less common than in other taxa. Amino acid replacement in a segment of the cytochrome b gene is faster in mammals and birds than in fishes and the pattern of replacements fits the structural hypothesis for cytochrome b. The unexpectedly wide taxonomic utility of these primers offers opportunities for phylogenetic and population research.