The methods employed to introduce recombinant DNA into host cell is/are

A. Micro-injection
B. Ligation
C. Cation treatment and heat shock
D. Gene gun

Choose the correct answer from the options given below:

A, C and D only

The correct answer is Option (3) → A, C and D only

A. In microinjection method, foreign DNA is indeed directly injected into the nucleus of an animal cell using microneedles. This is a technique used in genetic engineering to introduce foreign DNA into animal cells.

C. Cation treatment and heat shock: Treating cells (especially bacterial cells) with divalent cations (e.g., calcium ions) and applying a heat shock to make the cell membrane permeable, allowing DNA to enter.

D. Gene gun: Another technique, suitable for plants, cells are bombarded with high-velocity micro-particles of gold or tungsten coated with DNA. This method is known as biolistics or gene gun.

Ligation is not a method of introducing DNA into a host cell. Ligation refers to the process of joining DNA fragments together, usually with the help of DNA ligase.