Seleção genômica ampla em suínos usando o modelo de sobrevivência de Cox
Arquivos
Data
2013-02-26
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Universidade Federal de Viçosa
Resumo
A seleção genômica ampla (GWS) surgiu em 2001 com o objetivo de aumentar a eficiência e acelerar o ganho de seleção no melhoramento genético baseando-se exclusivamente em marcadores após terem seus efeitos genéticos estimados a partir de dados fenotípicos. No contexto de análise de sobrevivência, o modelo de riscos proporcionais de Cox com efeito aleatório foi comparado ao modelo linear misto, ambos usando a matriz de parentesco baseada em marcadores em substituição à baseada em pedigree, método esse denominado GBLUP. A aplicação foi feita aos dados reais de uma população F2 de suínos em que a variável resposta foi o tempo em dias, do nascimento até o abate do animal e as covariáveis: marcadores SNPs (238), sexo e lote de manejo. Os dados foram previamente corrigidos para seus efeitos fixos e a acurácia do método foi calculada com base na correlação dos postos dos valores genéticos genômicos preditos em ambos os modelos com os valores fenotípicos corrigidos. A análise foi repetida considerando menor número de marcadores SNPs que apresentassem maiores efeitos em módulo. Os resultados demonstraram concordância na predição dos valores genéticos genômicos e na estimação dos efeitos de marcadores para ambos os modelos na situação de dados não censurados e normalidade. No entanto, ao considerar a censura, o modelo de Cox com efeito aleatório normal foi o mais apropriado, uma vez que não houve concordância na predição dos valores genéticos genômicos e na estimação dos efeitos de marcadores com o modelo linear misto com dados imputados. A seleção de marcas permitiu um aumento nas correlações entre os postos dos valores genéticos genômicos preditos pelo modelo linear e pelo modelo de fragilidade de Cox com os valores fenotípicos corrigidos, sendo que para a característica analisada, 120 marcadores foram suficientes para maximizar a capacidade preditiva.
The genomic wide selection (GWS) emerged in 2001 with the goal of increasing efficiency and accelerating the selection gain in genetic improvement based exclusively on markers after their genetic effects estimated from phenotypic data. In the context of survival analysis, Cox s proportional risk model with random effects was compared to the mixed linear model, both using parenthood matrices based on markers in substitution to basing on pedigree, this method being named GBLUP. The application was made on real data from an F2 population of pigs in which the dependent variable was the time in days, from birth to slaughter of the animal and the covariables: SNP markers (238), sex and handled lot. The data was previously corrected for fixed effects and the accuracy of the method was calculated based on the correlation of the ranks of genomic genetic values predicted in both models with the phenotypic values corrected. The analysis was repeated considering the least number of SNP markers that presented the greatest effect in module. The results showed agreement in the prediction of genomic genetic values and estimation of the effects of markers for both models in the situation of uncensored data and normality. However, when considering censored data, the Cox model with normal random effect was more appropriate, since there was no agreement in the prediction of genomic genetic values and estimation of the effects of markers with the mixed linear model with imputed data. The selection of markers allowed an increase in correlations between the positions of genomic genetic values predicted by the linear model and the Cox frailty model with phenotypic values corrected, being that for the characteristic being analyzed, 120 markers were sufficient to increase the predictive power.
The genomic wide selection (GWS) emerged in 2001 with the goal of increasing efficiency and accelerating the selection gain in genetic improvement based exclusively on markers after their genetic effects estimated from phenotypic data. In the context of survival analysis, Cox s proportional risk model with random effects was compared to the mixed linear model, both using parenthood matrices based on markers in substitution to basing on pedigree, this method being named GBLUP. The application was made on real data from an F2 population of pigs in which the dependent variable was the time in days, from birth to slaughter of the animal and the covariables: SNP markers (238), sex and handled lot. The data was previously corrected for fixed effects and the accuracy of the method was calculated based on the correlation of the ranks of genomic genetic values predicted in both models with the phenotypic values corrected. The analysis was repeated considering the least number of SNP markers that presented the greatest effect in module. The results showed agreement in the prediction of genomic genetic values and estimation of the effects of markers for both models in the situation of uncensored data and normality. However, when considering censored data, the Cox model with normal random effect was more appropriate, since there was no agreement in the prediction of genomic genetic values and estimation of the effects of markers with the mixed linear model with imputed data. The selection of markers allowed an increase in correlations between the positions of genomic genetic values predicted by the linear model and the Cox frailty model with phenotypic values corrected, being that for the characteristic being analyzed, 120 markers were sufficient to increase the predictive power.
Descrição
Palavras-chave
Modelos mistos, GBLUP, Herdabilidade, SNPs, Mixed models, GBLUP, Heritability, SNPs
Citação
SANTOS, Vinicius Silva dos. Genomic Wide Selection (GWS) in pigs using the survival model of Cox. 2013. 88 f. Dissertação (Mestrado em Estatística Aplicada e Biometria) - Universidade Federal de Viçosa, Viçosa, 2013.