1 Bodega Marine Laboratory, University of California at Davis PO Box 247 Bodega Bay, CA 94923 2 Haskin Shellfish Research Laboratory,Institute of Marine and Coastal Science, Rutgers University, 6959 Miller Avenue, Port Norris, NJ 08349
Trisomy (2n+1) is an aneuploid condition where one chromosome is represented by three copies instead of the normal two copies. Change in copy number may affect the expression of genes located on the trisomic chromosome and therefore, analysis of trisomics may be useful for the chromosomal assignment of markers and quantitative trait loci. We produced trisomic families in the Pacific oyster, Crassostrea gigas Thunberg, and tested microsatellite markers for trisomic identification and analysis. Trisomic families were produced in two steps. First, diploid x triploid crosses were made, producing a mixture of normal diploids, triploids, trisomics and other aneuploids. Individuals with an approximate diploid DNA content were separated with flow cytometry and considered as putative trisomics. Then putative trisomics were crossed with each other or with normal diploids in single-pair matings. Sixty putative trisomic families were produced, and 20 of them were confirmed as trisomic families using chromosome counts of embryos at 2-cell stage. Parents from 16 trisomic families were screened with 14 microsatellite markers. Tri-allelism (3 alleles/locus/individual) was observed at three loci in six trisomic families. The tri-allelism was found only in the putative trisomic parent, not in normal diploids. One locus was tri-allelic in three of the 16 families, suggesting that the chromosome carrying this locus may be over-represented among the trisomic families. Progeny from the trisomic families are being analyzed for confirmation of trisomic inheritance. Results so far indicate that trisomic families can be readily produced, and microsatellite markers are useful in trisomic identification because of their high polymorphism.
Plant & Animal Genome VIII Conference Plant & Animal Genome VIII Conference