Gene markers

Gene linkage is a fundamental concept in 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. The principle of gene linkage was first observed by Thomas Hunt Morgan, an American geneticist and embryologist, in the early 20th century.

History

The concept of gene linkage was first proposed by William Bateson and Reginald Punnett after observing that certain traits tend to be inherited together more often than would be expected by chance. However, it was Thomas Hunt Morgan who provided the first experimental evidence of gene linkage in Drosophila melanogaster (fruit flies). Morgan's work on the linkage of genes led to the creation of the first genetic maps.

Mechanism

Gene linkage occurs because genes that are located close together on the same chromosome are less likely to be separated during chromosomal crossover, a process that occurs during meiosis. The closer two genes are to each other, the less likely they are to be separated by crossover events, and thus the more likely they are to be inherited together.

Linkage groups

A linkage group is a group of genes that are linked together on the same chromosome. The number of linkage groups in an organism is equal to the number of chromosome pairs. For example, humans have 23 linkage groups because they have 23 pairs of chromosomes.

Linkage map

A linkage map, also known as a genetic map, is a map of the relative positions of genes on a chromosome. The distance between genes is measured in centimorgans (cM), which is a unit of recombinant frequency. One cM is equivalent to a 1% chance that a marker at one genetic locus will be separated from a marker at a second locus due to crossover in a single generation.

Importance in genetics

Understanding gene linkage is crucial in many areas of genetics, including genetic counseling, genetic engineering, and evolutionary biology. It is also fundamental to the study of complex traits and genetic diseases, as these often involve the interaction of multiple genes that may be linked.

See also

• Genetic recombination
• Genetic linkage analysis
• Quantitative trait locus

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