Genetic linkage is the propensity of genes to be inherited together. During meiotic recombination, replicated chromosomes of each homologues pair align which allows homologues segments of DNA between the paternal and maternal chromatids to be exchanged. This process is known as crossing over. Because recombination occurs at random sites along the length of the chromosomes, the closer genes are together the less likely it is that they will be segregated onto separate chromatids (cross over). Genes that tend to be inherited together are said to be genetically linked.
Genetic linkage has been used to create genetic maps which allows for the determination of specific loci. These maps can play an important role in identifying where specific mutations are located on a chromosome allowing for the mutation and it's effect to be studied.
Lodish, H. Berk, A., Kaiser, C.A., Krieger, M., Scott, M.P., Bretscher, A., Ploegh H., Matsudaira, P. Molecular Cell Biology. 6th ed. New York: W.H. Freeman and Company, 2008. Print.