Strategies for genetic mapping of categorical traits |
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Authors: | Shaoqi Rao Xia Li |
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Institution: | (1) Department of Epidemiology and Biostatistics, Case Western Reserve University, Cleveland, Ohio 44106, USA;(2) Department of Epidemiology and Biostatistics, Case Western Reserve University, Cleveland, Ohio 44106, USA;(3) Department of Computer Science, Harbin Institute of Technology, Harbin, China, 150080 |
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Abstract: | The search for efficient and powerful statistical methods and optimal mapping strategies for categorical traits under various
experimental designs continues to be one of the main tasks in genetic mapping studies. Methodologies for genetic mapping of
categorical traits can generally be classified into two groups, linear and non-linear models. We develop a method based on
a threshold model, termed mixture threshold model to handle ordinal (or binary) data from multiple families. Monte Carlo simulations
are done to compare its statistical efficiencies and properties of the proposed non-linear model with a linear model for genetic
mapping of categorical traits using multiple families. The mixture threshold model has notably higher statistical power than
linear models. There may be an optimal sampling strategy (family size vs number of families) in which genetic mapping reaches
its maximal power and minimal estimation errors. A single large-sibship family does not necessarily produce the maximal power
for detection of quantitative trait loci (QTL) due to genetic sampling of QTL alleles. The QTL allelic model has a marked
impact on efficiency of genetic mapping of categorical traits in terms of statistical power and QTL parameter estimation.
Compared with a fixed number of QTL alleles (two or four), the model with an infinite number of QTL alleles and normally distributed
allelic effects results in loss of statistical power. The results imply that inbred designs (e.g. F2 or four-way crosses) with a few QTL alleles segregating or reducing number of QTL alleles (e.g. by selection) in outbred
populations are desirable in genetic mapping of categorical traits using data from multiple families.
This revised version was published online in July 2006 with corrections to the Cover Date. |
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Keywords: | categorical traits linear model mapping strategies mixture threshold model QTL allelic model |
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