TAILIEUCHUNG - Báo cáo sinh học: "Casein SNP in Norwegian goats: additive and dominance effects on milk composition and quality"

Tuyển tập các báo cáo nghiên cứu về sinh học được đăng trên tạp chí sinh học quốc tế đề tài: Casein SNP in Norwegian goats: additive and dominance effects on milk composition and quality | Dagnachew et al. Genetics Selection Evolution 2011 43 31 http content 43 1 31 GSE Ge n et i cs Selection Evolution RESEARCH Open Access Casein SNP in Norwegian goats additive and dominance effects on milk composition and quality Binyam S Dagnachew1 Georg Thaller2 Sigbjorn Lien1 3 and Tormod Ằdnoy1 Abstract Background The four casein proteins in goat milk are encoded by four closely linked casein loci CSN1S1 CSN2 CSN1S2 and CSN3 within 250 kb on caprine chromosome 6. A deletion in exon 12 of CSN1S1 so far reported only in Norwegian goats has been found at high frequency . Such a high frequency is difficult to explain because the national breeding goal selects against the variant s effect. Methods In this study 575 goats were genotyped for 38 Single Nucleotide Polymorphisms SNP located within the four casein genes. Milk production records of these goats were obtained from the Norwegian Dairy Goat Control. Test-day mixed models with additive and dominance fixed effects of single SNP were fitted in a model including polygenic effects. Results Significant additive effects of single SNP within CSN1S1 and CSN3 were found for fat and protein milk yield and milk taste. The allele with the deletion showed additive and dominance effects on protein and fat and overdominance effects on milk quantity kg and lactose . At its current frequency the observed dominance overdominance effects of the deletion allele reduced its substitution effect and additive genetic variance available for selection in the population substantially. Conclusions The selection pressure of conventional breeding on the allele with the deletion is limited due to the observed dominance overdominance effects. Inclusion of molecular information in the national breeding scheme will reduce the frequency of this deletion in the population. Background Under normal conditions the milk of mammals contains 30-35 g of protein per liter 1 . In the milk of ruminants more than 95 of these proteins

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