Mapping A QTL For Backfat On Porcine Chromosome 1 In A Complex Inbred Pig Family

~: P1~L~ 1 _ {4~J~ QTL ~3~31~ Mapping a QTL for Backfat on Porcine Chromosome 1 in a Complex Inbred Pig Family ABSTRACT A search for backfat QTL was carried out using 7 polymorphic microsatellite markers in a complex inbred pig family. The genotypes and allele sizes were analyzed using a PAGE with silver staining or denaturing PAGE with a DNA sequencer. Both multiple point analysis (MPA) and interval mapping (IM) were used to estimate the QTL effects and position. The results are summarized as below. 1 The æ…£OUCHDOWN?program was efficient for obtaining amplification of high yield and specificity. The PAGE with sliver staining was sensitive in detecting polymorphism but could be problematic in estimating the allele size. The denaturing PAGE with a DNA sequencer was efficient and accurate in marker genotyping and size estimation, as a result of using internal size t standards. 2 A genetic linkage map was constructed using CRIMAP V2.4 for QTL mapping that included 7 microsatellite markers, as below, SW552 (0.0) S0316 (25.9) --- SW2035 (52.8) S0113 (71.4) SW974 (87.3) --- S0056 (115.7) SWI3O1 (130.1) 3 A QTL for BFT was localized on porcine chromosome 1 (p < 0.01) The F ratio for the linked the marker or marker interval exceeded the 5% chromosome-wide significant threshold (p < 0.05) . Multiple point analysis mapped the QTL near the marker S0l13, and interval mapping localized it between S0113 and SW974. The estimated linkage position was 72.0 cM. 4 The additive and dominance effects of the QTL were 1.6965mm? 0.4092 and 2.1685mm?.4851, respectively, with multiple point analysis, and were 1.7036mm?.3393 and 2.413mm?.45555,respectively, with interval mapping. These estimates were very significantly different from zero (P < 0.01). The estimated QTL dominance effect exceeded the additive effect, WS: ~XA5P4tZt{t*W 1 fl~tflAhI QTL ~YWt5t indicating that this QTL followed dominant or over-dominant inheritance. 5 The QTL coincided with the VLDLR gene in linkage position and biological effect. It thus suggested that the VLDLR gene could be the candidate gene for the present QTL. Jiang Jun(Animal Gentic Breeding & Reproduction) Directed by Prof. Shi Qishun...