Question

A bacterium is infected with an experimentally constructed bacteriophage composed of the T2 phage protein coat and T4 phage DNA. The new phages produced would have

(A) T2 protein and T4 DNA.

(B) T4 protein and T2 DNA.

(C) T2 protein and T2 DNA.

(D) T4 protein and T4 DNA.

Short answer

(A) The statement “T2 protein and T4 DNA” is false.

(B) The statement “T4 protein and T2 DNA” is false.

(C) The statement “T2 protein and T2 DNA” is false.

(D)The statement “T4 protein and T4 DNA” is true.

Step-by-step solution

Step 1: Bacteriophage

Bacteriophage is a virus that uses bacterial cells for replication, which means it only infects bacteria. After infection in the bacteria, it attacks the host cellular machinery to produce viral components and assemble them into new bacteriophages.

The bacterial cell is lysed to release the virus particle in a lytic cycle. It also helps in bacterial transduction.

Explanation of option ‘(A)’

In the lytic cycle, the bacteriophage attaches to the bacterial cell surface with its tail fibres. Through contraction in a sheath of tails, the DNA of the bacteriophage is released in the host cell, and the capsid remains outside the cell.

This DNA produces a new copy of phage DNA and proteins that are used in assembling new bacteriophages. Here, a bacteriophage is composed of T4 phase DNA that is released in the bacteria after infection.

Thus,new phages after infection will produce T4 DNA and T4 proteins.

Therefore, the given statement is false.

Explanation of option ‘(B)’

T2 DNA will not be produced after the entry of a bacteriophage into a bacterial cell because the phage contains T4 DNA that will make its copy after capturing bacterial cell machinery. So T4 DNA will be produced.

Thus,T2 DNA will not be present in new phages produced after the lysis of the bacterial cells.

Therefore, the given statement is false.

Explanation of option ‘(C)’

The bacteriophage in the lytic cycle releases its content, that is, its DNA, into the bacterial host cell, and this DNA replicates and synthesizes protein by using host components. So the produced viral components will be similar to the DNA present in the bacteriophage.

Thus,newly produced bacteriophages will not have T2 DNA and T2 proteins.

Therefore, the given statement is false.

Explanation of option ‘(D)’

DNA in bacteriophage is T4 type that is the only component released in the host cell to make more bacteriophages. Therefore, it will make DNA and proteins similar to its type.

Thus, in new phages, T4 type DNA and proteins will be present.

Therefore, the given statement is true.