2.2 | Sample collection and DNA
isolation
Blood samples were obtained and genomic DNA was isolated using a blood
DNA extraction kit (TIANGEN, Beijing, China) and then stored at -20 ℃.
DNA integrity was evaluated by 1.5% agarose gel electrophoresis. The
most variable region in the mtDNA D-loop was assessed using data for
each of the samples. One female HGD was randomly selected to determine
the complete mtDNA sequence.