Quantitative trait locus

Quantitative trait locus (QTL) is a section of DNA (the locus) which correlates with variation in a phenotype (the quantitative trait). The QTL contains the alleles which are responsible for this variation. In the field of genetics, the term is used to identify the location and effect of genes that cause variation in the phenotype of a species.

Overview

A QTL is linked to a particular region of a chromosome and hence to specific genes. The number of QTLs which can be identified in a species depends on the amount of heritable variation that can be attributed to chromosomal regions. The resolution of the QTL mapping technique is limited, and there is often a region of uncertainty, which can span several megabases.

Identification

The identification of a QTL is based on the statistical correlation between genetic markers and phenotypic variation. This is usually done in specially bred populations which are segregating at many genetic loci. The use of markers in QTL mapping is a major feature that distinguishes this approach from traditional genetic methods.

Applications

QTL mapping has been used in a variety of species for the identification of genes that contribute to complex traits. These include traits that are of economic importance in agriculture, such as yield and disease resistance, as well as traits of evolutionary interest, such as the size and shape of flowers.

See also

• Genetic linkage
• Genetic marker
• Genome-wide association study
• Mendelian traits
• Polygenic inheritance

References

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Quantitative trait locus

• Example of QTL Scan on a single Chromosome
  Example of QTL Scan on a single Chromosome
• Example of a Genome-wide QTL Scan
  Example of a Genome-wide QTL Scan