Quantitative trait loci (QTL) for growth and egg traits were identified in chickens. After parentage checking, data of F2 chicks must be genotyped using genetic markers in the autosomal linkage groups and Z chromosome and the genotypes were used for QTL analysis. A mixed model included the fixed effects along with the additive and dominance effects of QTL as random effects were used for QTL analysis. In an Egyptian recent study, the total map length was 1901 cM for growth traits and 1949 cM for egg traits. A total of 34 QTL were detected for body weight traits (BW) where these QTL were distributed over five distinct regions on 10 chromosomes, and their effects ranged from 1.2 to 13.8% of the pheno¬typic variation. In this study, a total of 19 significant genome QTL that affected body weights were located on seven macro-chromosomes (1, 2, 3, 4, 6, 8 and Z) and one micro-chromosome (11). The proportions of phenotypic variation explained by significant and suggestive QTL for body weight traits at 4, 8, 12 and 16 weeks were 21.1, 30.8, 29.3 and 25.4%, respectively. The additive effects of QTL on growth traits were positive, while the dominance effects were generally negative or not significant. A QTL for body weight at 12 weeks of age segregating on chromosome 4 had the largest additive effect and explained 13.8% of the phenotypic variation, while the largest dominance effect for QTL on chromosome 4 and accounted for 6.5% of the phenotypic variation. The QTL effects were found on chromosomes 2, 4, 8 and Z for weight at first egg (WFE), on chromosomes 3 and Z for age at first egg (AFE), on the chromosomes 4 and Z for egg weight, on the chromosomes 4 and Z for egg number (EN). The QTL effects expressed as the percentage of the phenotypic variance explained by each QTL were mostly of considerable importance ranging from 1 to 6.9 % of the phenotypic variation for WFE, 5 to 7.2 % for AFE, 5.6 to 13 % for EW and 3.6 to 5 % for EN. The whole genome scan for detection and localization of QTL affecting egg quality traits were described. |
