Topic: Tools: restriction enzymes, vectors, host· Biotechnology and Its Applications

The following diagram showing restriction sites in E.coli cloning vector pBR322. Find the role of 'X' and 'Y' genes :

pBR322 plasmid map with restriction sites and genes X and Y

1. Gene 'X' is responsible for recognition sites and 'Y' is responsible for antibiotic resistance.

2. The gene 'X' is responsible for resistance to antibiotics and 'Y' for protein involved in the replication of Plasmid.

3. The gene 'X' is responsible for controlling the copy number of the linked DNA and 'Y' for protein involved in the replication of Plasmid.

4. The gene 'X' is for protein involved in replication of Plasmid and 'Y' for resistance to antibiotics.

Doubtly Asked 30 Oct 2026 NEET UG 2024 Practice test neet Save WhatsApp Report

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Answer: 3. The gene 'X' is responsible for controlling the copy number of the linked DNA and 'Y' for protein involved in the replication of Plasmid.

Key idea: pBR322 carries the origin of replication (ori), the rop gene and two antibiotic resistance genes (amp^R, tet^R).

On the map, X and Y are the two neighbouring markers at the bottom, away from the restriction sites that lie on the amp^R/tet^R genes. X is ori, which decides the copy number of the linked DNA. Y is rop, which codes for a protein involved in replication of the plasmid. This matches option 3.

Options 1, 2 and 4 are wrong because neither X nor Y is an antibiotic resistance gene or a recognition site.

Doubtly AI · 30 Oct 2026 AI-generated · not yet verified Report

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The following diagram showing restriction sites in E.coli cloning vector pBR322. Find the role of 'X' and 'Y' genes :

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