Figure 10.1: Many traits, such as body mass, show continuous variation, rather than discrete variation. Although environment obviously also affects this trait, some of the variation observed between individuals is heritable, and is dependent on the interactions of multiple alleles at multiple loci. The study of quantitative traits is one of many applications of molecular markers. (Flickr-Jamie Golombek-CC:AND)
- 10.1: Origins of Molecular Polymorphisms
- Some of mutations occur during DNA replication processes, resulting in an insertion, deletion, or substitution of one or a few nucleotides. Larger mutations can be caused by mobile genetic elements such as transposons, which are inserted more or less randomly into chromosomal DNA, sometimes occurring in clusters.
- 10.2: Classification and Detection of Molecular Markers
- Mutations that do not affect the function of protein sequences or gene expression are likely to persist in a population as polymorphisms, since there will be no selection either in favor or against them (i.e. they are neutral). Note that the although the rate of spontaneous mutation in natural populations is sufficiently high so as to generate millions of polymorphisms that accumulate over thousands of generations, the rate of mutation is slow.
- 10.3: Applications of Molecular Markers
- Several characteristics of molecular markers make them useful to geneticists. DNA polymorphisms are a natural part of most genomes. Geneticists discover these polymorphisms in various ways, including comparison of random DNA sequence fragments from several individuals in a population. Once molecular markers have been identified, they can be used in many ways.
- 10.4: Quantitative Trait Locus (QTL) Analysis
- We can use molecular markers to identify at least some of the genes (those with a major influence) that affect a given quantitative trait. This is essentially an extension of the mapping techniques we have already considered for discrete traits.
Dr. Todd Nickle and Isabelle Barrette-Ng (Mount Royal University) The content on this page is licensed under CC SA 3.0 licensing guidelines.