1Journal of Heredity 1998;89:1–7; 0022-1503/98/$5.00 Tandem Repeat Polymorphism and Heteroplasmy in the Mitochondrial Control Region of Redfishes

• Main Authors: P. Bentzen, J. M. Wright, L. T. Bryden, M. Sargent, K. C. T. Zwanenburg
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Orga; Newfoundland; Northwest Atlantic
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.594.2625; http://jhered.oxfordjournals.org/content/89/1/1.full.pdf

Three species of redfish (Sebastes) share a common pattern of mitochondrial DNA tandem repeat polymorphism and heteroplasmy in the northwest Atlantic Ocean. All three species exhibit 9–17 copies of an approximately 275 base pair (bp) tandem repeat situated within the 39 domain of the control region. Sequence analysis of cloned mtDNA from S. mentella revealed that the tandem array is adjacent to the tRNAphe gene, and that the repeat shares 53 % identity with the tRNAphe gene and part of the 12S rRNA gene. These features, as well as potential secondary structure assumed by the repeat, are consistent with previously proposed models explaining tandem duplications in the 39 end of the control region. In a sample comprising 36 S. fasciatus, 52 S. mentella, and 13 S. marinus taken near Newfoundland, neither the mean number of repeats per fish (12.2–12.7) nor the frequency of heteroplasmy varied significantly among species. A total of 42 % of the redfishes were hetero-plasmic, bearing either two or three repeat variants (33 % and 9%, respectively). The similarity of the frequency distributions of tandem repeat variants in the three species suggests either a common balance between mutation and selection in the three species, or mitochondrial gene flow between them. With a typical size of close to 16.5 kilobas-es (kb), more than 90 % of which consists of coding sequences, the compactly orga-nized vertebrate mitochondrial genome is generally regarded as having been shaped by selection for efficiency of function and replication (Rand 1993). Nonetheless, nu-merous examples of larger genomes have been observed, particularly in fishes (re-viewed in Billington and Hebert 1991) and other poikilotherms. In almost every case that has been sufficiently characterized, the ‘‘additional’ ’ DNA has been shown to consist of tandem repeats in the control region, the region that includes the D-loop and lies between the tRNAphe and tRNApro genes in most vertebrates (reviewed in