Mitochondrial DNA in natural populations: An improved routine for the screening of genetic variation based on sensitive silver staining

When screening natural populations for genetic variation in mitochondrial (mt) DNA it is necessary to screen as many individuals as possible for as large a number of base pairs as possible. This report describes a combination of laboratory techniques – isolation of mtDNA by either density ultracentrifugation or a phenol extraction procedure and DNA fragment visualization by a sensitive silver staining technique. These routines remove the major restriction of tissue sample size and number of individuals that can be screened and allows the investigation of at least 1000 base pairs from 1 g of tissue or 3–400 base pairs from 100 mg of frozen tissue.