Abstract
The objectives of this study were to examine problems with using F 1 data by simulation, association of marker loci and QTL from crosses of inbred parental lines and to enumerate the preliminary characterization of genetic superiority within inbred parental lines. In this study, the association between markers for QTL used as covariates and estimates of variance components due to effects of lines was investigated through computer simulation. The effects of size of population to develop inbred lines and initial frequencies and magnitudes of effects of QTL were also considered. Results show that estimates of variance components due to line effects are influenced by including marker information as covariates in the model for analysis. Estimates of line variance were increased by adding marker information into the analysis, because negative covariances between effects associated with the markers and the remaining effects associated with other loci existed. However, the fit of the model as indicated by the log likelihood improved by adding more markers as covariates into the analysis. Marker assisted selection will be beneficial when markers explain unexplained genetic difference during selection procedure. Markers can be used to identify QTLs affecting traits, and to select for favorable QTL alleles. To efficiently use genetic markers, location of markers at the genome must be identified. The estimates of variance due to effects of with and without marker information used as covariates in the analysis were investigated. The estimates of line variances were always increased when markers were included as covariates for the model because a negative covariance were existed.
Highlights
Advances in molecular genetics could provide quantitative geneticists and animal breeder with a better knowledge of the effects and locations of major loci, and an understanding of their actions and interactions that contribute to variation in quantitative traits
Many quantitative traits of economic importance are likely to be under the control of several genes, each with a relative small effect
Spelman and Garrick (1997) proposed that the majority of the genetic variance may be controlled by many genes with small effects even though there may be a few loci with large effects
Summary
Advances in molecular genetics could provide quantitative geneticists and animal breeder with a better knowledge of the effects and locations of major loci, and an understanding of their actions and interactions that contribute to variation in quantitative traits.Identifying marker-QTL associations may be undertaken from crosses of inbred lines or in segregating populations. Advances in molecular genetics could provide quantitative geneticists and animal breeder with a better knowledge of the effects and locations of major loci, and an understanding of their actions and interactions that contribute to variation in quantitative traits. Using genetic markers in conjunction with phenotypic observations would provide more information on the genetic merit of the animal than phenotypic information alone. Many quantitative traits of economic importance are likely to be under the control of several genes, each with a relative small effect. Most of the important traits may be controlled by more that one locus Often, these traits are influenced by the environment. Spelman and Garrick (1997) proposed that the majority of the genetic variance may be controlled by many genes with small effects even though there may be a few loci with large effects Many traits exhibit quantitative (continuous) variation. Spelman and Garrick (1997) proposed that the majority of the genetic variance may be controlled by many genes with small effects even though there may be a few loci with large effects
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