Population genetics of Atlantic cod using amplified single locus minisatellite VNTR analysis

Atlantic cod, Gadus morhua , have been examined extensively over the last two decades using allozyme electrophoresis. More recently, several populations have been studied using mitochondrial DNA (RFLP and sequence) analysis, together with multilocus minisatellite DNA and also microsatellite DNA analyses. The declining status of cod populations in many areas highlights the need for powerful genetic markers capable of discriminating between cod populations, in order to facilitate the design of effective management strategies. Single locus minisatellite DNA analysis offers a potentially powerful alternative to the already mentioned techniques, by combining the power of detection of hypervariable DNA, with non-radioactive techniques in a cost-effective way. As a preliminary investigation into the feasibility of using this approach, four Atlantic cod samples (North Norway, Irish Sea, Scotian Shelf and Northern Cod) were screened at a single polymerase chain reaction (PCR) amplified minisatellite locus ( Mmer -AMP2), using primers designed for the flanking regions of a whiting Merlangius merlangus L., minisatellite DNA locus. PCR products separated by agarose electrophoresis and viewed by ethidium bromide fluorescence under UV illumination, consisted of one or two bands per individual (corresponding to homozygotes and hétérozygotes, respectively). Twenty-two alleles were resolved in 119 cod, and sample heterozygosity ranged from 0.76 to 0.90. Samples from opposite sides of the Atlantic showed highly significant differences in allelic composition. The results suggest that single locus minisatellite DNA analysis may be of substantial benefit to furthering our knowledge of the population genetics of Atlantic cod.