Genes are present in a linear order along the chromosome. They are present in a specific location called locus (plural: loci). The diagrammatic representation of position of genes and related distances between the adjacent genes is called genetic mapping.
It is directly proportional to the frequency of recombination between them. It is also called as linkage map.
The concept of gene mapping was first developed by Morgan’s student Alfred H Sturtevant in 1913. It provides clues about where the genes lies on that chromosome.
The unit of distance in a genetic map is called a map unit (m.u). One map unit is equivalent to one percent of crossing over. One map unit is also called a centimorgan (cM) in honour of T.H. Morgan. 100 centimorgan is equal to one Morgan (M). For example: A distance between A and B genes is estimated to be 3.5 map units. It is equal to 3.5 centimorgans or 3.5 % or 0.035 recombination frequency between the genes.
Uses of genetic mapping
– It is used to determine gene order, identify the locus of a gene and calculate the distances between genes.
-They are useful in predicting results of dihybrid and trihybrid crosses.
– It allows the geneticists to understand the overall genetic complexity of particular organism.