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 bacteria. The new gene formed in this way is multiplied by the bacteria. This process is called gene cloning.

The cloned gene is thus used as per requirement:

1. Production of the required amount of protein by bacteria

2. 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 these, 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, which allows the insertion of new genes and transfer of the inserted genes to other organisms.

Main Steps in the Preparation of Recombinant DNA

1. Selection of the desired DNA (target DNA)

2. Selection of a carrier into which the desired DNA fragment can be transplanted (plasmid DNA is used)

3. Restriction for specific site cleavage of target and carrier DNA molecules

4. Annealing of DNA fragments (desired DNA and carrier) and joining 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 containing the desired DNA fragment

7. If Ti plasmid is used as a carrier: Transfection of the desired gene into the desired plant cell by Agrobacterium

Importance of Recombinant DNA Technology

Recombinant DNA technology is highly promising in the modern world. It enables genetic modification with wide applications in almost all areas of life.

Objectives of Crop Genetic Modification

1. Production of beneficial products: Addition of genes to crop plants so they can produce new beneficial products

2. Overcoming environmental resistance: Combination of genes to make crops tolerant to salinity, frost, drought, or other growth-limiting factors (e.g., salinity-tolerant peanut)

3. Invention of harmful insect-resistant varieties (Pest resistance): Gene integration produces substances toxic to insects (e.g., Bt cotton)

4. Development of herbicide-resistant varieties (Herbicide resistance): Incorporation of genes to allow herbicides to kill weeds without harming crops (e.g., glyphosate-resistant soybean)

Practical Uses of Recombinant DNA Technology

Agriculture

• Transgenic plants:

  • Example: Transgenic cotton plants produce a toxic protein from Bacillus thuringiensis, preventing insect attacks.

  • Benefits: Increased yields, reduced production costs, reduced soil, water, and air pollution.

  • Current adoption: 40% of corn, 50% of cotton, 45% of soybeans in America are transgenic varieties.

• Breeding:

  • Example: Sheep breeding in Australia for improved wool and meat quality.

• Super rice / Golden rice:

  • Problem: Vitamin A deficiency in children of rice-consuming countries

  • Solution: Swedish scientist Ingo Potrykus (1999) introduced beta-carotene and iron-producing genes into Japonica rice, preventing night blindness and anemia in children.

• Disease-resistant varieties:

  • Example: Tobacco plants transformed with the coat protein gene of the tobacco mosaic virus or potato virus are resistant to viral attacks.

Drugs Produced by Recombinant DNA Technology and Their Applications