A genetic map is a diagram of the mutual arrangement of structural genes, regulatory elements and genetic markers, as well as the relative distances between them on the chromosome (linkage group).
The farther apart the genes are located on the chromosome, the greater the likelihood of crossing over. Suppose the recombination frequency between genes A and B is 4%. This means that these genes are located on the same chromosome at a distance of four moribids. The crossover frequency between genes A and C is 10%, which means that gene C is located at a distance of 10 mb from gene A. It is still impossible to determine the relative position of getts A, B, and C based on these data, because genes B and C can be found as to the right and to the left of gene A in the chromosome. It is also necessary to know the crossover frequency of genes C and B. Suppose it is 6%, that is, genes C and B are located at a distance of six moribids. Now there is enough data to build a genetic map of the three genes. Genes A and C are most distant from each other, and gene B is located between genes A and C, since the distance AB + BC = AC,
To compile genetic maps, the crossover frequency of several genes is always analyzed.
For the unit of distance between genes, 1% of crossing-over is taken, this value is called a morganid (in honor of Morgan).
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