04-09-2012, 04:40 PM
Marker Assisted Selection
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Marker Assisted Selection
Marker assisted selection (MAS) is a combined product of traditional genetics and molecular biology. MAS allows for the selection of genes that control traits of interest. Combined with traditional selection techniques, MAS has become a valuable tool in selecting organisms for traits of interest, such as color, meat quality, or disease resistance.
BACKGROUND INFORMATION
Deoxyribonucleic acid (DNA) is a molecule made up of pairs of building blocks called nucleotides. The four kinds of nucleotides that make up DNA are adenine (abbreviated as the single letter A), guanine (G), cytosine ©, and thymine (T). The DNA molecule has the shape of two intertwined spirals, referred to as a double helix.
The sequence of nucleotides that make up a gene can differ among individuals. The different forms of a gene are called alleles. The alleles are the result of nucleotide differences in a gene that affect an amino acid sequence of a protein. This can result in a change, addition, or deletion of a protein that can affect the phenotype.
Molecular Markers
Until recently, researchers relied on information about how animals, plants, and their relatives perform to make observations about the genes they possess. Today, researchers can use molecular markers to find genes of interest that control how plants and animals perform. Some molecular markers are pieces of DNA that have no known function or impact on animal and plant performance. Other markers may involve the gene of interest itself.
Linked Markers
One type of molecular marker is called a linked marker.
Using well-designed experiments, scientists can find molecular markers that are located very close to major genes of interest. The molecular marker is said to be linked to that gene. Linked markers are only near the gene of interest on the chromosome and are not part of the DNA of the gene of interest.
Suppose that scientists are trying to locate a certain gene in an animal species. Choosing animals randomly from a population and studying them would give the scientists no clues about whether a marker is associated with the gene. However, if scientists studied the progeny (offspring) of the mating of male and female animals through many generations, they may determine the presence of a useful molecular marker.