Question

For which one of the following activities, the multiple copies of a specific gene/DNA sequence obtained through PCR can NOT be used for-

• A. Site directed mutagenesis
• B. Determination of sex of an embryo
• C. Estimation of recombination frequency
• D. In vitro regeneration of a complete organism

Hint:

Regeneration of an organism requires living, totipotent cells (tissue culture explants).
Naked DNA fragments amplified by PCR are chemical reagents and lack the cellular structure required to regenerate into a living organism.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
The Polymerase Chain Reaction (PCR) is an in vitro enzymatic method used to amplify a specific DNA sequence, producing millions of copies of the target DNA fragment.
These amplified DNA fragments are useful as molecular reagents for various genetic analyses and modifications.

Step 2: Detailed Explanation:
Let us evaluate each of the activities listed in the options:
- Site-directed mutagenesis (A) uses PCR primers containing specific nucleotide changes to introduce mutations into a target gene sequence, making PCR copies essential for this technique.
- Determination of the sex of an embryo (B) is performed by PCR-amplifying sex-specific chromosomal markers (such as Y-chromosome-specific sequences), where the presence or absence of the amplified product indicates sex.
- Estimation of recombination frequency (C) is routinely done by tracking and quantifying molecular markers (such as SSRs or SNPs) using PCR amplification in segregating populations.
- In vitro regeneration of a complete organism (D) is a physiological process that requires living cells or tissues (explants) containing the complete genome and functional cellular machinery (totipotency).
This process is achieved through plant tissue culture techniques (organogenesis or somatic embryogenesis) and cannot be accomplished simply using naked, amplified DNA copies in a test tube.

Step 3: Final Answer:
Therefore, PCR copies cannot be used for in vitro regeneration of a complete organism, corresponding to option (D).