Question

Main steps in the formation of Recombinant DNA are given below. Arrange these steps in a correct sequence.

1. Insertion of recombinant DNA into the host cell.
2. Cutting of DNA at specific location by restriction enzyme.
3. Isolation of desired DNA fragment.
4. Amplification of gene of interest using PCR. 

Choose the correct answer from the options given below:

Options

• C, A, B, D

• C, B, D, A

• B, D, А, C

• B, C, D, A

Answer 1

B, C, D, A

Explanation:

The process of creating recombinant DNA follows a precise sequence:

• Isolation and Purification: Genetic material is extracted from tissue and purified using specialised enzymes (like lysozyme for bacteria or cellulase for plants) to remove proteins, lipids, and other macromolecules.
• Restriction Digestion: Purified DNA is treated with restriction enzymes (molecular scissors) that recognise and cut the DNA at specific target sequences.
• Gene Amplification: The specific DNA fragment of interest is copied millions of times using Polymerase Chain Reaction (PCR), ensuring there is enough material for the next steps.
• Ligation: The amplified DNA fragment is mixed with a vector (like a plasmid) that has been cut with the same restriction enzyme. The enzyme DNA ligase then chemically joins these pieces together to form a stable recombinant DNA molecule.
• Insertion/Transformation: Finally, the engineered recombinant DNA is introduced into a host cell (typically a bacterium like E. coli) using methods such as heat shock, microinjection, or electroporation.