Results
ADD1
The ADD1 PCR fragment amplified in the pig was 95% homologous to the rat, and 83% homologous to human ADD1 sequence. Polymorphisms between the breed pools sequenced were also noted. Analysis of 27 porcine-rodent somatic cell hybrids (Yerle et al., 1996) determined regional assignment of ADD1 to porcine chromosome (SSC) 12 with 1.0 probability and to region 12p11-q15 with 0.95 probability (Figure 1). Results from the physical mapping in this study are in agreement with the localization of human ADD1 to HSA 17p11.2 (Hua et al., 1995), and chromosomal homologies between pig chromosome 12 and human chromosome 17 (Shi et al., 2000; Goureau et al., 1996). Other markers for meat quality have also been found on SSC 12 (Malek et al., 2000; Andersson-Eklund et al., 1996); therefore further analysis of genes on this chromosome is warranted.
A two-point linkage analysis was performed in five of the PiGMaP families (Archibald et al., 1995) using the CRI-MAP program (Green et al., 1990), and close linkage was found between ADD1 and markers previously mapped to the distal end of the q-arm of porcine chromosome 12, which confirms the physical mapping position of ADD1 (Figure 1). Further association studies utilizing the ADD1 PCR-RFLPs detected are planned in order to determine the effects of ADD1 on backfat and meat quality characteristics in the pig.
PDHA1
Analysis of 27 porcine-rodent somatic cell hybrids (Yerle et al., 1996) allowed regional assignment of PDHA1 to porcine chromosome (SSC) X with 1.0 probability and to region Xp22-p23 with 0.81 probability (Figure 1). Results from the physical mapping in this study are in agreement with the localization of the human pyruvate dehydrogenase E1-alpha subunit to HSA Xp22.2-Xp22.1 (Borglum et al., 1997). Quantitative trait loci (QTL) for backfat and production traits (Rohrer et al.,1998ab), as well as off flavor score (Malek et al., 2000) have also been reported on SSC X. Future linkage analysis to confirm the mapping location is planned, as well as, association studies to determine the effects of PDHA1 on meat quality in breed populations.
Summary
The addition of two new genetic markers (ADD1 and PDHA1) increases the information available on the pig genome, as well as provides potential new gene markers for the improvement of pork quality through marker assisted selection. Continued investigations with ADD1 and PDHA1 polymorphisms are planned in order to further define their effects on pork quality. Results of this study indicate there is great potential for the improvement of meat quality traits through the use of genetic markers in swine.