This is called genetic linkage. This linkage helps scientists to predict whether a plant will have a desired gene. If researchers can find the marker for the gene, it means the gene itself is present. As scientists learn where each of the markers occurs on a chromosome, and how close it is to a specific gene, they can create a map of the markers and genes on specific chromosomes. These genetic linkage maps show the location of markers and genes, and show their distance from other known genes.
Scientists can produce detailed maps in only one generation of plant breeding.
Previously, scientists produced very simple genetic maps using conventional techniques. However, since researchers could concentrate on only a few traits in each attempt at cross-breeding, it took many crosses to obtain even a very simple genetic map. Using very detailed genetic maps and better knowledge of the molecular structure of a plant's DNA, researchers can analyze a tiny bit of tissue from a newly germinated seedling. They don't have to wait for the seedling to grow into a mature plant so that they can test for a specific characteristic. Once the tissue is analyzed, scientists know whether that seedling contains the appropriate gene.