Submitted to: Genetics
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/22/2006
Publication Date: 11/1/2006
Citation: Phillips, R., Nichols, K., Dekoning, J., Morasch, M., Keatley, K., Rexroad III, C.E., Gahr, S.A., Danzmann, R., Drew, R., Thorgaard, G. 2006. Assignment of rainbow trout linkage groups to specific chromosomes. Genetics 174(3):1661-1670. Interpretive Summary: At NCCCWA we are constructing maps of chromosomes to identify genes that affect aquaculture production traits such as stress response, disease resistance, and feed efficiency. Constructing maps of chromosomes requires both physical and genetic mapping approaches. Part of physical mapping includes identifying chromosomes based on their size, shape, and ability to bind DNA probes containing a sequence of interest, perhaps a gene. Genetic maps are developed based on the biological phenomenon of recombination, the process by which parental chromosomes exchange genetic material to result in unique chromosomes for successive generations. Here we report the first integration of rainbow trout genetic and physical maps. As a result, maps generated to represent the genetic properties of a chromosome are linked to the physical chromosome they represent.
Technical Abstract: The rainbow trout genetic linkage groups have been assigned to specific chromosomes in the OSU (2N=60) strain using fluorescence in situ hybridization (FISH) with BAC probes containing genes mapped to each linkage group. There was a rough correlation between chromosome size and size of the genetic linkage map in cM for the genetic maps based on recombination from the female parent. Chromosome size and structure have a major impact on the female: male recombination ratio, which is much higher (up to 10:1 near the centromeres) on the larger metacentric chromosomes compared to smaller acrocentric chromosomes. Seventy-five percent of the BAC clones containing duplicate genes mapped to a single chromosomal location, suggesting that diploidization resulted in substantial divergence of intergenic regions. The BAC clones that hybridized to both duplicate loci were usually located in the distal portion of the chromosome. Duplicate genes were almost always found at a similar location on the chromosome arm of two different chromosome pairs, suggesting that most of the chromosome rearrangements following tetraploidization were centric fusions, and did not involve homeologous chromosomes. The set of BACs compiled for this research will be especially useful in construction of genome maps and identification of QTLs for important traits in other salmonid fishes.