Molecular Biology Questions and Answers – Various Classes of RNA Have Different Functions – 2

This set of Molecular Biology Questions and Answers focuses on “Various Classes of RNA Have Different Functions – 2”.

1. The 3’ end of tRNA is __________
a) 3’ CCA 5’
b) 3’ ACC 5’
c) 3’ CCG 5’
d) 3’ GCC 5’
View Answer

Answer: b
Explanation: All tRNA has a conserved sequence of 3’ ACC 5’. This sequence is conserved so as to facilitate cognate amino acid binding.

2. Thymine is present in tRNA.
a) True
b) False
View Answer

Answer: a
Explanation: Some unusual bases are present in the tRNA for its improved functioning. One of such pos – transcriptional modification is done enzymatically is the presence of thymine base in place of uracil in the primary structure.

3. With respect to tRNA which of the following is not its characteristic?
a) Complimentary region
b) Double helix molecule
c) Highly conserved pattern of fold
d) Variable loop
View Answer

Answer: b
Explanation: The complementary region enables the tRNA to form limited stretches of double helix held together by base pairing. The other stretches of the tRNA are non – complementary thus remain single stranded as loops. Thus the tRNA is a mixture of single and double stranded regions represented by the clover leaf model.
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4. How many loops are present in the clover leaf model of tRNA?
a) 2
b) 3
c) 4
d) 5
View Answer

Answer: c
Explanation: There are 4 loops and an acceptor stem in the clover leaf model of tRNA. The names of the 4 loops are ΨU loop, D loop, anticodon loop and the variable loop.

5. Why the variable loop is named so?
a) Variable number of bases
b) Variable region
c) Multiple loops present
d) Variability of presence
View Answer

Answer: a
Explanation: The variable loop sits between the anticodon loop and the ΨU loop and its region is fixed. The name is so given because they vary in size from 3 to 21 bases.
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6. The distance between the amino acid binding site and the anticodon site is ______
a) 64 Å
b) 70 Å
c) 76 Å
d) 80 Å
View Answer

Answer: b
Explanation: X – ray crystallography reveals the tRNA has an L – shaped tertiary structure. In this structure, the amino acid binding site o acceptor site is approximately 70 Å away from the anticodon site residing on the opposite end of the structure.

7. What is the angle between the D loop and the anticodon loop?
a) 45˚
b) 90˚
c) 135˚
d) 180˚
View Answer

Answer: b
Explanation: The X – ray crystallography shows that the D loop and the ΨU loop comes together making the anticodon loop an extended helix. These to helices align at right angle, that is, 90˚ to each other in their tertiary structure.
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8. Which of the following does not contribute to the stability of tRNA?
a) Base and sugar-phosphate backbone interaction
b) Hydrogen bonding
c) Hydrophobic interactions
d) Base pairing
View Answer

Answer: c
Explanation: Due to the negative charge of the tRNA backbone, it is unlikely for the molecule to have a hydrophobic nature. Thus, hydrophobic interactions do not play any role in the structural stability of the molecule. On the other hand, the other interactions such as the hydrogen bonding lead to base pairing which leads to its classic clover leaf model.

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Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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