Inheritance and expression in diploid and triploid Chinook salmon (Oncorhynchus tshawytscha): Segregation distortion at the major histocompatibility complex (MHC) and microsatellite loci

In order to investigate the influence of triploidy on genetic inheritance and expression, DNA and mRNA were extracted from diploid and triploid offspring of a single breeding pair of Chinook salmon. Neutral (microsatellite) and a functional markers (class I major histocompability complex (MHC)) were used to analyze the DNA samples for meiotic bias. Significant segregation distortion (P<0.02) was found in the distribution of maternal-origin alleles in the triploid samples at two microsatellite loci and at the MHC locus. No bias was found in the diploid samples, indicating that the distortion was due to maternal dosage effects. This could be the result of a biochemical imbalance caused by dilution of the paternally-derived gene product, or to gene dosage effects of functional, deleterious, maternally-derived proteins. MRNA, converted to cDNA, was also used as a template for MHC amplification and, as expected, the MHC expression in the triploid offspring displayed a dosage effect pattern.