The concept of linkage is very important to the field of genetics.
Linkage occurs when two or more genes exist close together on the same chromosome.
Genes that are close together form linkage groups and are often inherited together. Sometimes the linked genes can be separated by the process of crossing-over which occurs during meiosis. This will produce different genetic combinations than exist in the parent. This process is called genetic recombination and is partially responsible for the genetic variation which exists in sexually reproducing animals. Linkage can also be used to identify individuals carrying deleterious genes, even if the gene itself cannot be detected.