This set of Cell Biology Multiple Choice Questions & Answers (MCQs) focuses on “Gene Expression – Translation”.
1. The synthesis of polypeptide can be divided into ______ distinct activities.
a) 1
b) 2
c) 3
d) 4
View Answer
Explanation: The synthesis of polypeptides, termed as translation, involves 3 distinct activities: initiation of the chain, elongation of the chain, and termination of the chain.
2. Which of the following moves in consecutive blocks of three nucleotides?
a) ribosome
b) ribozyme
c) polymerase
d) helicase
View Answer
Explanation: On the messenger RNA strand, the ribosome moves along the mRNA from one codon to the next in the consecutive blocks of three nucleotides.
3. Which of the following is an initiation codon?
a) AAA
b) AUG
c) AGU
d) AGG
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Explanation: Initiation codon, AUG, is the site where the ribosome machinery attaches itself on the mRNA strand. Attaching to the initiation codon puts the ribosome in the proper reading frame of translation.
4. Shine-Dalgarno sequence is present in the ____________________
a) hnRNA
b) mRNA
c) tRNA
d) siRNA
View Answer
Explanation: The Shine-Dalgarno sequence is present 5-10 nucleotides upstream of the initiation codon in the bacterial mRNA. The 16S ribosomal RNA has a complementary sequence for it which leads to the binding of 30S small ribosomal subunit on the mRNA strand.
5. Initiation factors are ______________________
a) lipids
b) soluble proteins
c) lipopolysaccharides
d) phospholipids
View Answer
Explanation: Initiation factors are the soluble proteins that help in initiating the polypeptide chain formation. Bacterial cells have three initiation factors IF1, IF2, and IF3.
6. The first amino acid incorporated at the N-terminus of polypeptide is ___________________
a) methionine
b) cysteine
c) tryptophan
d) valine
View Answer
Explanation: The initiation codon AUG, codes for the amino acid methionine. It is the first amino acid to be incorporated at the N-terminus of a nascent polypeptide, in bacteria it is formylmethionine.
7. What drives the conformational change in the ribosome?
a) GTP hydrolysis
b) AMP hydrolysis
c) ATP hydrolysis
d) GDP hydrolysis
View Answer
Explanation: The large ribosomal subunit joins the mRNA strand when initiator tRNA is bound and IF3 is displaced. After a large subunit joins the complex, GTP is hydrolyzed to drive the conformational change in the ribosome so as to release IF2.
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