Recombinant DNA Technology : Steps, Application and Future

Recombinant DNA technology

Recombinant DNA technology is the genetic engineering technology that can bring about desired structural changes in an organism's DNA. In this method, a part of the DNA molecule with a specific gene is cut outside the cell and replaced in the plasmid DNA of the bacteria. The new gene formed in this way is multiplied by the bacteria. It is called gene cloning.

The cloned gene is thus used as per requirement, i.e.

(i) production of the required amount of protein by bacteria and

(ii) introduction into other desired organisms, especially plants.

Producing transgenic plants through the expression of the new gene is then observed in the organism. Recombinant DNA technology is a new branch of biology. It started in the mid-1970s, but human society has already benefited from it.

Recombinant DNA technology and transgenic plant production processes are mainly dependent on microorganisms. Among the mentioned microorganisms, bacteria like E. coli, Agrobacterium tumefaciens, etc., are widely used. A unique feature of these bacteria is that their cells contain a small circular DNA molecule in addition to the main chromosome. This extra circular DNA is called a plasmid. Plasmids allow the insertion of new genes and transfer the inserted genes to other organisms.

The main steps in the preparation of recombinant DNA are as follows: 

1. Selection of the desired DNA (target DNA).
2. Selection of a carrier into which the desired DNA fragment can be transplanted. In this case, plasmid DNA is used.
3. Restrictions required for specific site cleavage of target and carrier DNA molecules.
4. The annealed DNA fragments (desired DNA and carrier) are joined by the DNA ligase enzyme. 
5. Selection of a host (e.g., E. coli) for replication of the carrier DNA with the desired DNA. 
6. Expression evaluation of recombinant DNA prepared to contain the desired DNA fragment.
7. If Ti plasmid is used as a carrier during the preparation of recombinant DNA
8. Transfection of the desired gene into the desired plant cell by Agrobacterium.

Recombinant DNA technology is the most talked about and highly promising technology in the present world. The possibilities of this technology are wide open in almost all areas of life. It causes genetic modification.

Objectives of Crop Genetic Modification

1. Production of beneficial products: The addition of genes to crop plants so that the plant can produce a new beneficial product (which the plant could not produce before). 

2. Overcoming environmental resistance: The combination of genes makes it more tolerant to salinity, frost, drought, or any other regulator that limits crop growth. E.g., the Development of salinity tolerant 'Peanut.'

3. Invention of harmful insect-resistant varieties (Pest resistance): Gene integration that is capable of producing toxic substances that can cause the death of insects and spiders harmful to crops. Like- Bt.cotton. 

4. Development of herbicide-resistant varieties (Herbicide resistance): Incorporation of genes so that application of herbicides will kill the weeds but will not harm the crops. For example, developing soybean plants resistant to glyphosate.

Practical Uses of Recombinant DNA technology

Recombinant DNA technology is being used successfully in agriculture; such as

Transgenic plants

The cotton bollworm attack on American cotton plants causes yearly yield loss. Insecticides had to be used to prevent insect attacks. Transgenic cotton plants have been created by adding a gene from the bacterium Bacillus thuringiensis. These transgenic cotton plants produce a toxic protein for insects, preventing insect attacks. This has resulted in increased cotton yields, reduced production costs due to the absence of pesticides, and reduced soil, water, and air pollution on the land. Currently, 40 percent of corn, 50 percent of cotton, and 45 percent of soybeans grown in America are transgenic varieties. But cotton, golden rice, and late blight disease-resistant potato cultivation trials are also going on in Bangladesh, but it has not been given at the farmer level yet.

Breeding

Sheep breeding in Australia is a good business for quality improvement, so wool and meat are obtained from sheep.

Super rice or Golden rice

Children of various Asian countries are deficient in vitamin A. A lack of vitamin A-rich foods usually causes this. So, if we can fill up the lack of vitamin A through rice, our children will not be night-blind or blind. Keeping this objective in mind, Swedish scientist Ingo Potrykus (1999) and his colleagues invented Super Rice. They replaced four beta-carotene-producing genes and three additional iron-producing genes from daffodils with Japonica-type rice.

By eating this rice, millions of boys and girls in the rice-loving communities of Asia, Africa, and Latin America will no longer be blind due to vitamin-A deficiency. Some will be saved from various diseases caused by anemia in the body. 

Development of disease-resistant varieties:

Recombinant DNA technology has successfully developed varieties resistant to viruses, bacteria, fungi, and various types of insects. Tobacco plants transformed with the coat protein gene of the tobacco mosaic virus, potato virus, are resistant to virus attack.

Drugs produced by recombinant DNA technology and their applications