Linkage (genetics)

Linkage (genetics) is a fundamental concept in the field of genetics that refers to the tendency of DNA sequences that are close together on a chromosome to be inherited together during the meiosis phase of sexual reproduction.

Overview

The concept of linkage was first introduced by the British geneticist William Bateson and his colleagues, including Reginald Punnett, in the early 20th century. They observed that certain traits tend to be inherited together, which contradicted the independent assortment principle proposed by Gregor Mendel. This led to the discovery of genetic linkage and the development of the first genetic maps.

Mechanism

Linkage occurs because the likelihood of a gene being separated from its neighboring gene during chromosomal crossover is proportional to the distance between them. Therefore, genes that are close together on a chromosome are more likely to be inherited together. This is known as the principle of linkage disequilibrium.

Linkage Mapping

Linkage mapping is a method used to determine the relative position of genes on a chromosome. It is based on the observation that the frequency of recombination between two genes is proportional to the distance between them. This allows geneticists to construct a genetic map that represents the sequence of genes on a chromosome.

Linkage and Disease

Understanding genetic linkage is crucial in the study of genetic diseases. For instance, if a disease trait and a marker gene are inherited together, it suggests that they are linked and close together on the chromosome. This information can be used to identify the location of genes that cause genetic diseases, a process known as positional cloning.

See Also

• Genetic recombination
• Genetic linkage analysis
• Genome-wide association study
• Quantitative trait locus