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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.
Map Distance Over Long Chromosomes. Map distances are always calculated for one pair of loci at a time. However, by combining the results of multiple pairwise calculations, a genetic map of many loci on a chromosome can be produced (Figure 11.2.2). A genetic map shows the map distance, in cM, that separates any two loci, and the position of ...
Genetic maps are useful for showing the order of loci along a chromosome, but the distances are only a relative approximation. The correlation between recombination frequency and actual chromosomal distance is more accurate for short distances (low RF values) than long distances.
Physical maps specify the distances between landmarks along a chromosome. Ideally, the distances are measured in nucleotides, so that the map provides a direct description of a chromosomal DNA molecule. The most important landmarks in physical mapping are the cleavage sites of restriction enzymes.
A linkage map (also known as a genetic map) is a table for a species or experimental population that shows the position of its known genes or genetic markers relative to each other in terms of recombination frequency, rather than a specific physical distance along each chromosome.
Genome mapping is the process of finding the locations of genes on each chromosome. The maps created by genome mapping are comparable to the maps that we use to navigate streets. A genetic map is an illustration that lists genes and their location on a chromosome.
There are two main ways to map a genome: genetic mapping and physical mapping. They’re used to identify and record the location of genes and the distances between genes on a chromosome. A genome map highlights the key ‘landmarks’ in an organism’s genome, helping scientists to navigate their way around the genome as they sequence it.
