Variation in the copy number of tandem repeats of mitochondrial DNA in the North-East Atlantic cod populations

Abstract

The variation in copy number of short tandem repeats located within the control region of mitochondrial DNA and heteroplasmy is characterised in four populations of Atlantic cod (Gadus morhua) in the North-eastern Atlantic. Populations of cod from three geographic areas (the Barents Sea, the North Sea and the Baltic Sea) were sampled. Published data on Icelandic cod were included for comparison. Nineteen length heteroplasmy patterns were found. Individuals carried up to five distinct size variants. Size variants 465 bp and 505 bp were most common (frequency 0.269 and 0.301, respectively). The 425 bp size variant in a few heteroplasmy patterns was present more frequently in the population from the Barents Sea than from other areas. Widespread heteroplasmy displays geographical variation in the Atlantic. The L pattern of heteroplasmy seems to be characteristic of the Baltic population.