250+ TOP MCQs on Genes Are Expressed by Making RNA – 2 and Answers

Molecular Biology Multiple Choice Questions on “Genes Are Expressed by Making RNA – 2”.

1. The β subunit of polymerase has a function of ____________
A. Promoter binding
B. Catalytic center
C. Template binding
D. Cation binding

Answer: B
Explanation: The β subunit of polymerase is thought to be its catalytic center. Studies suggested that the β subunit may contain two domains responsible for transcription initiation and elongation.

2. Presence of the heparin promotes transcription.
A. True
B. False

Answer: B
Explanation: A poly heparin has been shown to bind to the β’ subunit. Heparin inhibits transcription invitro and also competes with DNA for binding to polymerase.

3. The β’ subunit of polymerase has a function of ________________
A. Promoter binding
B. Elongation
C. Cation binding
D. Termination

Answer: C
Explanation: The β’ subunit of polymerase binds to two Zn²⁺ ions which are thought to participate in the catalytic function of the polymerase. It is also responsible for the binding of the enzyme to the template DNA.

4. The RNA polymerase core enzyme converts into a holoenzyme on the addition of the _________ subunit.
A. α
B. β
C. β’
D. σ

Answer: D
Explanation: Binding of the σ factor converts the core RNA polymerase enzyme into the holoenzyme. The σ factor has a critical role in promoter recognition but is not required for transcription elongation.

5. Four types of σ factors are known of them which one is heat stable?
A. σ⁷⁰
B. σ³²
C. σ⁵⁴
D. σ²⁸

Answer: A
Explanation: σ⁷⁰ is the most common σ factor.
σ³² is highly heat stable.
σ⁵⁴ is used during N₂ deficiency.
σ²⁸ is used for chemotaxis.

6. What is the function of the ω subunit of RNA polymerase?
A. Subunit association
B. Promoter binding
C. Initiation and elongation
D. Cation binding

Answer: A
Explanation: The ω subunit of RNA polymerase helps in the association of all the subunits. Promoter binding is promoted by α subunit. Initiation and elongation is promoted by the β subunit. And β’ subunit binds to the Mg²⁺ cations.

7. Which of the following is not part of the RNA polymerase core enzyme?
A. α
B. β
C. ω
D. σ

Answer: D
Explanation: The σ subunit is not part of the RNA polymerase core enzyme. The RNA polymerase core protein has the structural formula of α₂ββ’ω. Addition of the σ subunit converts the RNA polymerase core protein into a holoenzyme.

8. The bacterial system has _____________ RNA polymerases.
A. 1
B. 2
C. 3
D. 4

Answer: C