This set of Protein Engineering Multiple Choice Questions & Answers (MCQs) focuses on “t-RNA and its Aminoacylation”
1. Which of the following is also known as the “adaptor” molecule?
a) hnRNA
b) rRNA
c) mRNA
d) tRNA
View Answer
Explanation: tRNA carries a specific amino acid and recognizes the corresponding mRNA codon with the help of the anticodon loop. Hence, tRNA is also known as an “adaptor” molecule.
2. Almost all known tRNA can be schematically arranged in which of the following secondary structures?
a) Planar
b) Beta-sheet
c) Helical
d) Cloverleaf
View Answer
Explanation: Almost all known tRNA can be schematically arranged in cloverleaf secondary structures. Moreover, a tRNA has a 5’ terminal phosphate group. Beta-sheets and helical structures are present in the secondary structure of proteins.
3. The amino acid carried by the tRNA is covalently attached to its 5’ terminal end?
a) True
b) False
View Answer
Explanation: The amino acid carried by the tRNA is covalently attached to its 3’ terminal OH group. There is also a phosphate group on the 5’ terminal end. This arm is also known as the amino acid binding arm.
4. ψ is the symbol of which amino acid?
a) Psuedocytosine
b) Pseudoguanidine
c) Pseudoadenine
d) Pseudouridine
View Answer
Explanation: ψ is the symbol ofpseudouridine. It is an unusual amino acid occurring in a particular loop of tRNA. Hence, the arm containing this loop is called as Tψ C or T arm.
5. Where in the structure of tRNA, occurs a site of greatest variability?
a) Anticodon loop
b) D arm
c) Tψ Cloop
d) Variable arm
View Answer
Explanation: Variable arm is a site of greatest variability in the structure of tRNA. It has around 3 to 21 nucleotides. Apart from this arm, there are other arms in tRNA like amino acid acceptor arm, anticodon arm, Tψ C arm, and D arm.
6. Which of the following shape is assumed by the tertiary structure of tRNA?
a) O shaped
b) I shaped
c) T shaped
d) L shaped
View Answer
Explanation: All tRNA molecules have an L shaped complex tertiary structure. In this structure Tψ C arm and amino acid acceptor arm form one leg and the D and anticodon arm form the other.
7. Which of the following enzymes attach amino acids to tRNA?
a) Amino acyl-tRNA reductase
b) Amino acyl-tRNA synthase
c) Amino acyl-tRNA ligase
d) Amino acyl-tRNA synthetase
View Answer
Explanation: Amino acyl-tRNA synthetase selects the correct amino acid for covalent attachment to a tRNA. It only attaches the correct amino acid to the tRNA for which it is specific. Thus, like tRNAs, amino acyl-tRNA synthetases are also of different specificities.
8. Proteins are made by incorporating standard amino acids. How many standard amino acids are there in nature?
a) 19
b) 22
c) 21
d) 20
View Answer
Explanation: There are 20 standard amino acids in nature. Proteins are made by incorporating these amino acids. But, two other amino acids apart from these are also known to be incorporated in protein during translation.
9. Which of the following amino acid is known as the 21st amino acid?
a) Pseudouridine
b) Dihydrouridine
c) Lysidine
d) Selenocysteine
View Answer
Explanation: Selenocysteine is known as the 21st amino acid. It is a non-standard amino acid. Twenty standard amino acids are incorporated into proteins. There are two non-standard amino acids, and selenocysteine is one of them.
10. In the protein synthesis, which of the following interaction results in attachment of correct amino acid?
a) Amino acid – tRNA interaction
b) Amino acid – anticodon interaction
c) Amino acid – codon interaction
d) Codon – anticodon interaction
View Answer
Explanation: In the protein synthesis, codon-anticodon interaction results in attachment of correct amino acid to the polypeptide sequence. The aminoacyl group does not participate in this process. Codon and anticodon are complementary to each other.
11. Who proposed the wobble hypothesis?
a) Louis Pasteur
b) Gregor Mendel
c) Francis Collins
d) Francis Crick
View Answer
Explanation: Francis Crick proposed the wobble hypothesis. The wobble hypothesis accounts for the degeneracy of codon. It explains how a tRNA can recognize several degenerate codons.
12. Wobble pairing occurs in which of the following positions?
a) All positions
b) First position
c) Second position
d) Third position
View Answer
Explanation: Wobble pairing occurs in the third position with reference to 5’-3’ orientation of the mRNA. In the third pairing, a limited conformational adjustment is allowed.
13. Find the odd one out?
a) Alanine
b) Cysteine
c) Methionine
d) Selenocysteine
View Answer
Explanation: Selenocysteine is a non-standard amino acid. Alanine, cysteine, and methionine are standard amino acids. Thus, selenocysteine is the odd one out. It is also termed as the 21st amino acid.
14. Which among the following sequence is present at the 3’ terminal of all tRNA?
a) CCC
b) CAC
c) ACC
d) CCA
View Answer
Explanation: CCA is the sequence that is present at the 3’ terminal of all tRNA. It is also responsible for the binding of amino acid to tRNA. Therefore, it constitutes the amino acid acceptor arm.
15. Which of the following is a uracil derivative nucleotide?
a) 3-methyl cytidine
b) Lysidine
c) Inosine
d) Pseudouridine
View Answer
Explanation: Pseudouridine is uracil derived nucleotide. It is present in a loop of tRNA in the sequence Tψ C. Hence, that loop is also known as the Tψ C loop. 3-methyl cytidine, lysidine, and inosine are not uracil derived nucleotides.
Sanfoundry Global Education & Learning Series – Protein Engineering.
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