This study covered two main areas in the methodology of Quantitative Trait Locus (QTL) detection with the use of genetic markers: i) the use of sib pair analysis for QTL detection in animal populations of large family size and ii) the use of selective genotyping in sib pair analysis for the reduction of genotyping costs. The regression of the squared phenotypic differences of sib pairs on the proportion of alleles they share Identical By Descent (IBD) at a marker locus can provide a test of linkage between a marker and a QTL. The t-values of the regression coefficient can provide a way to detect linkage. The regression coefficient can provide estimates of the QTL position and variance. The power of detection and parameter estimates (position and QTL variance) obtained from the analysis of progeny originating from populations with different family size, were compared using simulated data. Families of large size provide large numbers of sib pairs, since the number of sib pairs is related to the family size. The correlation of phenotypic differences between sib pairs of the same family has little effect on the test statistic and consequently on the power of detection. In order to decrease the amount of genotyping without any negative effects on the power of detection, a different approach to sib pair analysis was used. Instead of using the associations between phenotypic differences and proportion of alleles shared IBD at a marker locus for the detection of linkage, any changes in the proportion of alleles shared IBD at a marker locus in a selected sample of phenotypically discordant sib pairs could be used to identify linkage between the marker and a QTL. The t-values of the regression constant were used to test any deviations of the mean proportion of alleles shared IBD at a marker locus from the expected mean (0.5). It was found that this is the most powerful test statistic in samples of sib-pairs selected for high phenotypic differences.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:642768 |
| Date | January 1998 |
| Creators | Chatziplis, Dimitrios |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/14410 |
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