This set of Molecular Biology Multiple Choice Questions & Answers focuses 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
View Answer
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
View Answer
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
View Answer
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
View Answer
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
View Answer
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
View Answer
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
View Answer
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
View Answer
Explanation: The bacterial system has 3 RNA polymerases. They are RNA polymerase I, RNA polymerase II and RNA polymerase III. RNA polymerase I transcribes mRNAs, and RNA polymerases II and III transcribe the other specialized RNAs.
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