Development and characterization of DNA sequence OmyP9 associated with thesex chromosomes in rainbow trout

This work describes the construction and characterization of a sequence cha racterized amplified DNA region (SCAR DNA), designated OmyP9, that was deri ved from a RAPD marker associated with the sex chromosomes in rainbow trout . A RsaI restriction fragment length polymorphism in OmyP9 identifies varia nts A, B and C. We found six OmyP9 variant phenotypes - A, B, C, AB, BC and ABC, in 186 individuals of seven different rainbow trout strains. The patt erns of inheritance of OmyP9 in 139 fingerlings from 10 crosses of three st rains of rainbow trout were studied. The males had a greater representation of the A variant (93.3%) suggesting an association with the Y Chromosome. All male fingerlings analysed inherited the A variant from their male paren ts. These results support the hypothesis that OmyP9 is located on the sex c hromosomes of rainbow trout, and that for the males Studied the A variant i s located on the Y chromosome in a region close to sex determinants and/or in a sector where the genetic recombination between X and Y is restricted. The present evidence also supports our previous hypothesis that OmyP9 is or ganized as a tandem repeated sequence in the sex chromosomes of rainbow tro ut. We feel that the OmyP9 RsaI marker can be used for sex identification i n crosses where it is possible to determine the phenotype of the parents.