Nucleotide sequence and evolutionary conservation of a minisatellite variable number tandem repeat cloned from Atlantic salmon, Salmo salar

We describe the nucleotide sequence, extent of polymorphism, and evolutionary conservation of a minisatellite cloned from a fish, Atlantic salmon (Salmo salar). The Ssal minisatellite contains a 16-bp repeat exhibiting partial sequence identity to bird and mammal minisatellites but most closely resembling an insect minisatellite (81% sequence identity). The Ssal locus exhibits a minimum of three to seven alleles per population in three eastern North American salmon populations. A probe based on the nonrepetitive 5' flank of Ssal detected a polymorphic locus in a variety of salmoid species, suggesting that this locus has persisted in its polymorphic state for >25 million years. Multiple polymorphic bands detected by the same probe suggest the presence in salmonid genomes of additional minisatellite loci that are related to Ssal either through the tetraploidization of the salmonid genome or some other mechanism of gene duplication.