The following diagram showing restriction sites in E coli cloning vector pBR322. Find the role of 'X' and 'Y' genes:
Answer: (A) The gene 'X' is responsible for controlling the copy number of the linked DNA and 'Y' for protein involved in the replication of plasmid.. Answer: (A) The gene 'X' is responsible for controlling the copy number of the linked DNA and 'Y' for protein involved in the replication of plasmid.
- A.The gene 'X' is responsible for controlling the copy number of the linked DNA and 'Y' for protein involved in the replication of plasmid.✓
- B.The gene 'X' is for protein involved in replication of plasmid and 'Y' for resistance to antibiotics.
- C.Gene 'X' is responsible for recognition sites and 'Y' is responsible for antibiotic resistance.
- D.The gene 'X' is responsible for resistance to antibiotics and 'Y' for protein involved in the replication of plasmid.
Correct Answer
(A) The gene 'X' is responsible for controlling the copy number of the linked DNA and 'Y' for protein involved in the replication of plasmid.
Solution & Explanation
Answer: (A) The gene 'X' is responsible for controlling the copy number of the linked DNA and 'Y' for protein involved in the replication of plasmid. Solution: In pBR322, the origin of replication (ori) is the sequence responsible for controlling the copy number of the linked DNA, while rop codes for the proteins involved in the replication of the plasmid. Hence X (ori) controls copy number and Y (rop) encodes the replication protein — matching option A. Options invoking antibiotic resistance for X or Y are wrong because resistance is conferred by the separate ampR and tetR genes. NCERT Reference: Ch 9, p.169, line(s) 9 & 60-62 — "responsible for controlling the copy number of the linked DNA" ... "rop codes for the proteins involved in the replication of the plasmid."