Genome Mapping: Objectives, Types and Concept

In this article we will discuss about Genome Mapping:- 1. Objectives of Genome Mapping 2. Types of Genome Maps 3. Fundamental Concept 4. Benefits.

Contents:

1. Objectives of Genome Mapping
2. Types of Genome Maps
3. Fundamental Concept of Genetic Mapping
4. Benefits of Genetic Mapping

1. Objectives of Genome Mapping:

In a Genomic Map we Aim at Finding out Fol­lowing Two Things:

a. The determination of linear order with which genetic units are arranged with respect to one another (gene order). For example, if there are three genes A, B and C then a genetic map determines their or­der of arrangement, i.e., whether they are arranged as ABC, ACB, BCA, BAC, CAB or CBA.

b. To determine relative distance between genetic units (gene distance).

2. Types of Genome Maps:

Depending on above two objectives there are two types of genome maps:

I. Genetic Maps:

This is also called as link­age map. A genetic map is representa­tion of genes on a chromosome arrayed in linear order with distances between loci expressed as per cent recombination (map units, centimorgans).

II. Physical Maps:

A physical map de­scribes the physical location of genes on chromosomes.

3. Fundamental Concept of Genetic Mapping:

The possibility of genetic recombination in meiosis tends to occur with increasing fre­quency as the distance between two specific gene loci on a chromatid. The percentage of genetic recombination can be used to repre­sent a measure of distance (map distance) be­tween the two genes.

The frequency of cross­ing over (per cent recombination) between two loci is directly related to the physical distance between the loci. One unit of map distance is, therefore, equivalent to one per cent crossing over. Map units are often referred to as centimorgans (cM) in honour of the work of Thomas Hunt Morgan, a famous drosophila geneticist.

If two loci are 1 cM apart, then a crossover occurs between them only in every 100 meio­sis on an average. Thus,

1 map unit = 1cM and 1cM = 1% recom­bination.

If two genes recombine with a frequency of 2.5%, then they are said to be located 2.5 map units apart. In humans 1cM is approxi­mately equal to 1 × 10⁶ bp.

4. Benefits of Genetic Mapping:

The techniques developed for genetic mapping have had great impact on the life sciences, and particularly in medicine. But genetic mapping technologies also have useful applications in other fields. Commercialization of the fruits of genomics research promises immense op­portunities for industry.

A round-up of genetic mapping applications would include (but not be limited to) the areas below:

a. Medicine:

Scientists have become more proficient in genetic sequencing the de­tailed genetic maps that help locate the risk genes for a host of genetic diseases. The ability to investigate the root cause of diseases may one day allow medical re­searchers to develop strategies to avoid the environmental conditions that serve as triggers to disease, formulate customized drugs, and techniques for gene therapy.

b. Agricultural Applications:

Knowledge of the genetic maps of plants and animals leads to the development of agricultural crops and animal breeds that are more nutritious, productive and can better re­sist diseases, insects and drought. Re­searchers can breed special plants that help clean up wastes that are difficult to break down.

c. Energy and the Environment:

Genetic maps of microbes enable researchers to harness the power of bacteria for produc­ing energy from bio-fuels, reducing toxic waste, and developing environment- friendly products and industrial processes.

d. Forensics:

Gene mapping is used in crime investigations, paternity tests, and iden­tification. The technique can also be used in organ transplants to achieve better matches between recipients and donors, thus minimizing the risks of complications and maximizing the use of donated healthy organs, a scarce resource.