DNA sequences linked with a particular trait of interest that are faithfully inherited over generations without being affected by the environment. Molecular markers are like landmarks on chromosomes that can direct us to select for a particular trait. Testing for the presence of a marker directly selects for a trait of interest. Selection based on molecular markers (marker-assisted selection MAS) can be cost-effective. A large number of plants can be monitored for the presence of a gene or desirable trait by a marker in the lab instead of erratic testing in the field.