15: Molecular Markers and Quantitative Traits
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)
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- 15.1: Some Variations in the Genome Affect Complex Traits
- This page discusses the similarities and differences in the genomic DNA sequences of two individuals, noting that while many variations occur in non-coding regions and may not have a functional impact, they are valuable as molecular markers. These markers play important roles in medicine, forensics, and agriculture, allowing for the creation of genetic maps and the identification of linked genes.
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- 15.2: 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.
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- 15.3: 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.
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- 15.4: 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.
Contributors
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Dr. Todd Nickle and Isabelle Barrette-Ng (Mount Royal University) The content on this page is licensed under CC SA 3.0 licensing guidelines.