title: A directed search for quantitative trait loci on chromosomes 4 and 7 in pigs.
abstract: Improvements in the porcine genetic map and availability of resource families to study performance traits in pigs have made it possible to re-examine previous findings that linked certain traits to genes or chromosomal regions. Previous studies suggested that chromosomes 4 and 7 may be associated with growth and performance traits. To confirm these previous results, an interval mapping-regression approach was used to determine whether quantitative trait loci (QTL) exist in the Iowa State University reference/resource families. Traits measured were birth weight; body weight at 21 d; weaning weight (weight at 42 d); average daily gain; backfat at the first, 10th, lumbar, and last ribs and average backfat thickness; loin eye area; meat color; marbling; and firmness. The total number of F2 pigs used ranged from 241 to 330 and came from five Chinese x American resource families. Five markers (S0001, SW871, S0175, S0214, and SW445) were genotyped and mapped on chromosome 4, and so were 10 markers (S0064, tumor necrosis factor alpha [TNFalpha], S0102, S0078, S0158, S0066, SW304, SW1083, S0101, and S0212) on chromosome 7. Data were analyzed for each family (breed cross) separately and were also pooled. Experiment-wise thresholds were used to determine significance. Suggestive evidence of QTL on chromosomes 4 and 7 was observed for several traits in pooled and individual family analyses. Suggestive evidence of a QTL with a relatively large effect for average daily gain was detected on chromosome 4 in the pooled analysis. Significant (P < .05) evidence for QTL was seen on chromosome 7 for 10th-rib, last-rib, and average backfat thickness in the pooled data set in a region of the chromosome that was near TNFalpha. These results verify in part that chromosomes 4 and 7 contain QTL for growth and carcass traits.
authors.affiliation: Department of Animal Science, Iowa State University, Ames 50011, USA.
authors.forename: L
authors.initials: L
authors.lastname: Wang
authors.forename: T P
authors.initials: TP
authors.lastname: Yu
authors.forename: C K
authors.initials: CK
authors.lastname: Tuggle
authors.forename: H C
authors.initials: HC
authors.lastname: Liu
authors.forename: M F
authors.initials: MF
authors.lastname: Rothschild
mesh_terms: D000818:Animals; D001724:Birth Weight / Q000235:genetics; D002874:Chromosome Mapping; D003433:Crosses, Genetic; D005260:Female; D008297:Male; D008460:Meat / Q000592:standards; D018895:Microsatellite Repeats; D013552:Swine / Q000235:genetics* / Q000254:growth & development; D014886:Weaning; D015430:Weight Gain / Q000235:genetics*