Question

The following diagram shown restriction sites in E. coli cloning vector pBR322. Find the role of ‘X’ and ‘Y’gens :

• A. The gene ‘X’ is responsible for resistance to antibiotics and ‘Y’ for protein involved in the replication of Plasmid.
• B. The gene ‘X’ is responsible for controlling the copy number of the linked DNA and ‘Y’ for protein involved in the replication of Plasmid.
• C. The gene ‘X’ is for protein involved in replication of Plasmid and ‘Y’ for resistance to antibiotics
• D. Gene ’X’ is responsible for recognitions sites and ‘Y’ is responsible for antibiotic resistance

Answer 1

The Correct Option is B

Step 1: Understanding the function of the 'X' and 'Y' genes:

The E. coli plasmid pBR322 contains two important genes, labeled 'X' and 'Y', which play crucial roles in the replication and stability of the plasmid. These genes are vital in controlling the copy number and maintenance of the plasmid within bacterial cells.

Step 2: Role of gene 'X' (ori):

The 'X' gene in the diagram represents the origin of replication, denoted as ori. The origin of replication is a specific sequence where the replication process begins. It controls the copy number of the linked DNA, ensuring that the plasmid replicates efficiently within the bacterial cell.

Step 3: Role of gene 'Y' (rop):

The 'Y' gene corresponds to rop, which codes for a protein involved in plasmid replication. The rop protein helps in the stabilization of plasmid replication by regulating the number of plasmid copies. It plays a role in the maintenance of the plasmid during cell division.

Step 4: Conclusion:

Therefore, in the given diagram:

• 'X' is ori: The origin of replication, controlling the copy number of linked DNA.
• 'Y' is rop: A gene coding for a protein involved in plasmid replication.

Incorrect Options: Options (1), (3), and (4) are incorrect because the roles assigned to 'X' and 'Y' in these options do not correspond to the functions of the origin of replication (ori) and the rop gene.

Answer: The correct answer is Option 1.

Answer 2

To determine the roles of genes 'X' and 'Y' in the E. coli cloning vector pBR322, we need to consider the functions of common genes found in such vectors. In the context of pBR322, 'X' and 'Y' likely refer to genes involved in important plasmid functions:

Gene 'X': It is responsible for controlling the copy number of the linked DNA. This means that the gene helps regulate how many copies of the plasmid, and hence the inserted DNA, are produced within the bacterial cell. This is crucial for ensuring that there is enough plasmid DNA for the bacteria to maintain antibiotic resistance and for replication processes.

Gene 'Y': This gene is involved in the replication of the plasmid. It encodes for a protein essential for the duplication of the plasmid's DNA, ensuring that the plasmid is copied and passed on to daughter cells during bacterial cell division.

Therefore, the correct answer is: The gene ‘X’ is responsible for controlling the copy number of the linked DNA and ‘Y’ for protein involved in the replication of Plasmid.