Question

Given below are two statements, one is labeled as Assertion (A) and other one labeled as Reason (R).
Assertion (A) : Bacterial artificial chromosome is useful for the synthesis of RNA used for in vitro translation.
Reason (R) : Bacterial artificial chromosome is F factor based cloning vector possessing SP6 and T7 promotor.
In light of the above statements, choose the correct answer from the options given below.

• A. Both (A) and (R) are true and (R) is the correct explanation of (A).
• B. Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
• C. (A) is true but (R) is false.
• D. (A) is false but (R) is true.

Hint:

BACs are based on the F-plasmid replicon to maintain a strict copy number of 1 to 2 plasmids per cell.
This low copy number is critical to prevent recombination and maintain the stability of large cloned genomic DNA fragments in E. coli.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Bacterial Artificial Chromosomes (BACs) are specialized low-copy-number cloning vectors designed to clone and maintain very large segments of genomic DNA (up to 300 kb) in E. coli.
Detailed Explanation:
- Evaluating Assertion (A): BACs are genomic library vectors designed for physical mapping, genomic sequencing, and functional genomic analysis.
They are not used for synthesizing RNA for in vitro translation.
Small, high-copy-number transcription/expression plasmids (such as pGEM or pBluescript vectors) containing specific promoter sequences are designed and used for in vitro transcription and translation. Thus, Assertion (A) is false.
- Evaluating Reason (R): BAC vectors are constructed using the replication machinery of the single-copy E. coli fertility plasmid (F-factor).
They incorporate specific bacteriophage promoters, such as SP6 and T7, flanking the cloning site to allow the generation of RNA transcripts from the ends of the cloned genomic inserts. Thus, Reason (R) is true.

Step 2: Final Answer:
Assertion (A) is false but Reason (R) is true. This corresponds to option (D).