MOLECULAR MARKERS

MOLECULAR MARKERS - Molecular markers have the potential of increasing the efficiency and quality of the selection for desirable traits in new varieties. A molecular marker assisted selection allows breeders to handle larger populations while selecting earlier traits unaffected by the environment, and with more assurance for the desired trait. Molecular markers identify genetic differences linked to a specific trait. The best marker is the identification of the actual gene/genes associated with the trait. However, identifying the gene for a particular characteristic from the huge amount of DNA within an organism is a daunting task and many traits are not simply inherited and are dependent on several genes. Therefore, researchers often rely on gene linkages. Some types of molecular markers are listed below:
• Isozymes: differences in the genes that code for or regulate enzyme synthesis or activity
• Restriction fragment length polymorphisms (RFLPs): differences in the sites at which restriction enzymes can cut the DNA
• Random amplified polymorphic DNA (RAPDs): differences in the sites at which DNA will be amplified by the polymerase chain reaction (PCR)
• Amplified fragment length polymorphisms (AFLPs): differences in restriction sites & PCR amplification
• Simple sequence repeats (SSRs) or microsatellites: differences in repetitive DNA sequences