Materials & Methods
Candidate Gene Association Studies
The population utilized for the project consisted of both purebred and crossbred animals from the 1998 National Barrow Show Progeny Test and the 1999 Hampshire Sire Progeny Test. All animals were managed by identical protocols, and performance, carcass, meat quality, and sensory panel measurements were taken on each animal. Individuals of four major U.S. breeds were chosen for DNA extraction from frozen loin chops. Berkshire (n=180), Duroc (n=77), Hampshire (n=160), and Landrace (n=55) sire breeds were represented. Genotypes were obtained for six candidate genes using Polymerase Chain Reaction _ Restriction Fragment Length Polymorphism (PCR-RFLP) procedures unique for each gene analyzed. Statistical analyses were performed within each breed separately, and across breeds for the total population. Only pigs classified as free of the Porcine Stress Syndrome mutation were utilized in these analyses. A SAS (1999) Mixed Model analysis was completed for the total population and a within breed analysis. Allelic frequencies were calculated within breed and for the total population based upon observed genotype classifications.