Question

What is chromosome mapping?

Answer 1

Hint: A chromosome is a long DNA molecule with part or all of the genetic material of an organism. Most eukaryotic chromosomes include packaging proteins called histones which, aided by chaperone proteins, bind to and condense the DNA molecule to maintain its integrity.

Complete answer:
In autosomal DNA testing, chromosome mapping is a technique that helps the test to decide which segments of DNA came from which ancestor.It is important to test a number of close relatives in order to map DNA segments on particular chromosomes.
A recombination frequency of less than 50% for a pair of genes in Dihybrid genetic crosses has been identified as indicating linkage, i.e., being on the same chromosome. Morgan and Sturtevant discovered that the frequency of recombination differs between mutant gene pairs.

The mutant's black body (b) and vestigial wings (vg), for example, had a recombination frequency of 18%, while black body (b) and cinnabar eye (cn) had a recombination frequency of 9%. As a result, cross-over between b and vg is twice as common as between b and cn.

The gap between the genes was found to be related to the difference in recombination frequencies. Cross-over occurs more often in genes further apart on a chromosome than in genes closer together. As a result, the gap between b and vg should be roughly twice as large as the distance between b and cn. As a result, recombination frequencies can aid in the identification of loci, genes in chromosomes, and the preparation of chromosome maps.

As a result, a chromosome map is a graphic representation of a linkage group in the form of a line that displays the sequence of genes and the relative distances between the genes it contains using points. A chromosome map is also known as a genetic map or a linkage map. Chromosome mapping is the process of creating a species' chromosome map.

Chromosome mapping is based on the two genetic concepts mentioned below. They really are –

1. The genes are arranged in a chromosome in a linear order.
2. That the distance between two genes on the chromosome is directly proportional to the frequency of crossing over between them. Since chromosome maps are created using the frequency of crossing over, they are also known as cross over maps.

Chromosome map unit:One unit of map distance between two genes is known as a Morgan after T. H. Morgan, and it is defined as a frequency of one percent crossing over between these genes.

Note: Drosophila, rice, and Neurospora chromosome maps were developed first. Linkage maps have now been produced for a number of other species. Certain viruses' chromosome maps, as well as the circular DNA of certain bacteria, have been prepared using a slightly different technique.