Chromosome map

Chromosome map is a diagrammatic representation of the linear sequence of genes on a chromosome. The concept of a chromosome map was first proposed by Alfred Sturtevant, a student of Thomas Hunt Morgan, in the early 20th century.

History

The first chromosome map was created by Alfred Sturtevant in 1913. He used the fruit fly, Drosophila melanogaster, as a model organism to study genetics. Sturtevant's work was based on the observation that the frequency of genetic recombination between genes is proportional to their physical distance on the chromosome. This led to the development of the concept of a genetic map.

Construction

The construction of a chromosome map involves several steps. First, the genetic markers are identified. These markers can be genes or other DNA sequences that have a known location on the chromosome. The distance between these markers is then determined using genetic recombination data. The more frequently two markers are separated by recombination, the further apart they are assumed to be on the chromosome.

Types of Chromosome Maps

There are three main types of chromosome maps: genetic maps, physical maps, and cytogenetic maps.

• Genetic maps are based on the frequencies of recombination between markers during meiosis. The unit of measurement on a genetic map is the centimorgan (cM), which corresponds to a 1% chance of recombination occurring between two markers.

• Physical maps are based on the actual physical distances between markers, usually measured in base pairs. These maps are constructed using techniques such as restriction mapping and sequence mapping.

• Cytogenetic maps are based on the visible features of chromosomes, such as banding patterns. These maps are constructed using techniques such as karyotyping and fluorescence in situ hybridization (FISH).

Applications

Chromosome maps have a wide range of applications in genetics and genomics. They are used in gene discovery, genetic screening, genome sequencing, and comparative genomics. They also play a crucial role in the study of genetic diseases and genetic variation.

See Also

• Genetic linkage
• Genome mapping
• Human Genome Project
• Molecular genetics