Quantitative trait loci mapping

Both twin studies and quantitative trait loci mapping methods have provided evidence for a significant genetic contribution to the risk of developing a substance dependence disorder. However, both of these lines of research have underscored the importance of environmental factors. A rich body of preclinical work has demonstrated that stress delivered at a wide range of time points in development can modulate proclivity towards drug self-administration. Evidence has suggested... 

Berrettini, W.H., Ferraro, T.N., Alexander, R.C., Buchberg, A.M., and Vogel, W.H. (1994) Quantitative trait loci mapping of three loci controlling morphine preference using inbred mouse strains. Nat Geneti 7 54-58. 

Kliebenstein DJ, Gershenzon J, Mitchell-Olds T (2001) Comparative quantitative trait loci mapping of aliphatic, indolic and benzylic glu-cosinolate production in Arabidopsis thaliana leaves and seeds. Genetics 159 359-370. 

Durrant, C., Mott, R., 2010. Bayesian quantitative trait locus mapping using inferred haplotypes. Genetics 184, 839-852. 

These findings were unexpected because previous studies had demonstrated that the y2 subunit is required for potentiation of GABAa receptor function by low concentrations of ethanol [2]. The y2 subunit gene is located within a definitely mapped quantitative trait locus (QTL) for acute alcohol withdrawal on mouse chromosome 11 [1]. Allelic variation was genetically... 

Simko, L, Costanzo, C., Haynes, K. G., Christ, B. J., Jones, R. W. (2004a). Linkage disequilibrium mapping of a Verticillium dahliae resistanee quantitative trait locus in tetraploid potato (Solanum tuberosum) through a candidate gene approach. Theoretical and Applied Genetics, 108,2X1-224. 

A more recent application of microarray is in the quantitative trait locus (QTL) mapping area. The conventional analysis of QTL is on phenotypic traits such as blood pressure and body weight, which are measured from each individual in a genetic segregating family of individuals resulting from crosses or pedigrees. In recent... 

Fischer, B.M., Salakhutdinov, I., Akkurt, M., Eibach, R., Edwards, K.J., Tbpfer, R., Zyprian, E.M., 2004. Quantitative trait locus analysis of fnngal disease resistance factors on a molecular map of grapevine. Theor. Appl. Genet. 108, 501-515. 

Liang T, Spence J, Liu L, et al. a-Synuclein maps to a quantitative trait locus for alcohol preference and is differentially expressed in alcohol-preferring and -nonpreferring rats. Proc Natl Acad Sci USA. 2003 100 4690-4695. 

A major problem of such approaches is that they have extremely low statistical power. For example, for a tightly linked marker (0 = 0) to trait-related locus which in turn accounts for as much as 15% of the variance in the quantitative trait (Fa = 0.15) Sham et al. (55) estimated that 5322 sib pairs would be needed. Although a number of twin cohorts with very extensive phenotyping exist (4) which could potentially be used for linkage studies, the low statistical power involved renders them less attractive for mapping QTLs. 

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