Atypical mitochondrial DNA from the deep-sea scallop Placopecten magellanicus

The mitochondrial DNA of most metazoan animals is highly conserved in size, averaging about 17 kilobase paris (kbp). The mitochondrial DNA from the deep-sea scallop Placopecten magellanicus, in contrast, has been found to be approximately 34 kbp long. It is also highly variable in size from individual to individual and is unusual in the extent of its size variation. Mitochondrial DNAs from individuals collected at the same site differ by as much as 7 kbp. The size variation is due largely to differences in the number of copies of a tandemly repeated 1.2-kbp element.