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Quantitative trait loci - Definition and Overview |
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Quantative trait loci (QTL) are sets of genes at specific places (loci, singular locus) in the genotype (the genetic information encoded in a species' DNA) which control a particular phenotype (specific aspect of the species' physical development).
The different sets of genes which may appear in any one specific locus are called alleles. The set of different combination of alleles which appear at all the sites in the QTL control the final resulting expression of the trait in the phenotype. Typically this trait varies continously as opposed to a discrete trait such as smooth or wrinkled peas as in Mendel's experiments.
The QTL techniques were developed in the late 1980s and can be performed on inbred strains of any species.
QTL mapping
QTL mapping is the statistical study of the alleles which occur in a locus and the phenotypes (physical forms or traits) that they produce. Because most traits of interest are governed by more than one gene, defining and studying the entire locus of genes related to a trait gives hope of understanding what effect the genotype of an individual might have in the real world.
Statistical analysis is required to prove that different genes interact with one another, and to determine whether they are producing a significant effect in the phenotype.
QTLs identify a particular region of the genome as containing a gene that is associated with the trait being assayed or measured. They are shown as intervals across a chromosome, where the probability of association is plotted for each marker used in the mapping experiment.
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