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10.S: Molecular Markers and Quantitative Traits (Summary)
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- Natural variations in the length or identity of DNA sequences occur at millions of locations throughout most genomes.
- DNA polymorphisms are often neutral, but because of linkage may be used as molecular markers to identify regions of genomes that contain genes of interest.
- Molecular markers are useful because of their neutrality, co-dominance, density, allele frequencies, ease of detection, and expression in all tissues.
- Molecular markers can be used for any application in which the identity of two DNA samples is to be compared, or when a particular region of a chromosome is to be correlated with inheritance of a trait.
- Many important traits show continuous, rather than discrete variation.These are also called quantitative traits.
- Many quantitative traits are influenced by a combination of environment and genetics.
- The heritable component of quantitative traits can best be studied under controlled conditions, with pure-breeding parents that are polymorphic for both a quantitative trait and a large number of molecular markers.
- Molecular markers can be identified for which specific alleles are tightly correlated with the quantitative value of a particular phenotype.The genes that are linked to these markers can be identified through subsequent research.