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By finding recombination frequencies for many gene pairs, we can make linkage maps that show the order and relative distances of the genes on the chromosome.
A genetic map (or recombination map) is a representation of the linear order of genes (or loci), and their relative distances determined by crossover frequency, along a chromosome. The fact that such linear maps can be constructed supports the concept of genes being arranged in a fixed, linear order along a single duplex of DNA for each chromosome.
A genetic map shows the map distance, in cM, that separates any two loci, and the position of these loci relative to all other mapped loci. The genetic map distance is roughly proportional to the physical distance, i.e., the amount of DNA between two loci.
Genetic mapping is a way to identify exactly which chromosome has which gene and exactly pinpointing where that gene lies on that particular chromosome. Mapping also acts as a method in determining which gene is most likely to recombine based on the distance between two genes.
The genetic map distance is roughly proportional to the physical distance, i.e., the amount of DNA between two loci. For example, in Arabidopsis , 1.0 cM corresponds to approximately 150,000 bp and contains approximately 50 genes.
The genetic map distance is roughly proportional to the physical distance, i.e., the amount of DNA between two loci. For example, in Arabidopsis, 1.0 cM corresponds to approximately 150,000 bp and contains approximately 50 genes. The exact number of DNA bases in a cM depends on the organism, and on the particular position in the chromosome.
Physical Maps. A physical map provides detail of the actual physical distance between genetic markers, as well as the number of nucleotides. There are three methods scientists use to create a physical map: cytogenetic mapping, radiation hybrid mapping, and sequence mapping.
