This set of Bioinformatics Multiple Choice Questions & Answers (MCQs) focuses on “Types of RNA Structures”.
1. RNA structures can be experimentally determined using _____
a) X-ray crystallography techniques only
b) NMR techniques only
c) X-ray crystallography or NMR techniques
d) Gel electrophoresis
Explanation: However, the two approaches are extremely time consuming and expensive. As a result, computational prediction has become an attractive alternative. Option Gel electrophoresis, here, becomes irrelevant as it comes to the structure of RNA.
2. Which of the following is not a form of RNA?
Explanation: It is known that RNA is a carrier of genetic information and exists in three main forms. They are messenger RNA (mRNA), ribosomal RNA (rRNA), and transfer RNA (tRNA). Their main roles are as follows: mRNA is responsible for directing protein synthesis; rRNA provides structural scaffolding within ribosomes; and tRNA serves as a carrier of amino acids for polypeptide synthesis.
3. Unlike DNA, which is mainly double stranded, RNA is double stranded, although an RNA molecule can self-hybridize at certain regions to form partial double-stranded structures.
Explanation: RNA is single stranded, although an RNA molecule can self-hybridize at certain regions to form partial double-stranded structures. Generally, mRNA is more or less linear and non-structured, whereas rRNA and tRNA can only function by forming particular secondary and tertiary structures.
4. Structures are not much important when it comes to the study of the functions.
Explanation: Knowledge of the structures of these molecules is particularly important for understanding their functions. Difficulties in experimental determination of RNA structures make theoretical prediction a very desirable approach. In fact, computational-based analysis is the main tool in RNA-based drug design in pharmaceutical industry. In addition, knowledge of the secondary structures of rRNA is key for RNA-based phylogenetic analysis.
5. Which of the following is not a base of RNA?
a) Thymine (T)
b) Adenine (A)
c) Cytosine (C)
d) Guanine (G)
Explanation: RNA structures can be described at three levels as in proteins: primary, secondary, and tertiary. The primary structure is the linear sequence of RNA, consisting of four bases, adenine (A), cytosine (C), guanine (G), and uracil (U).
6. Base pairing, in RNA, is A–G and U–C.
Explanation: The secondary structure refers to the planar representation that contains base-paired regions among single-stranded regions. The base pairing is mainly composed of traditional Watson–Crick base pairing, which is A–U and G–C.
7. In addition to the canonical base pairing, there often exists non-canonical base pairing such as _________ and ________ base paring.
a) G, U
b) G, C
c) U, C
d) A, C
Explanation: There often exists non-canonical base pairing such as G and U base paring. The G–U base pair is less stable and normally occurs within a double-strand helix surrounded by Watson–Crick base pairs. Finally, the tertiary structure is the three-dimensional arrangement of bases of the RNA molecule.
8. Four main subtypes of secondary structures can be identified. They are hairpin loops, bulge loops, interior loops, and multi-branch loops.
Explanation: Because the RNA tertiary structure is very difficult to predict, attention has been mainly focused on secondary structure prediction. Based on the arrangement of helical base pairing in secondary structures, the mentioned four main subtypes of secondary structures can be identified.
9. The ______ refers to a structure with two ends of a single-stranded region (loop) connecting a base-paired region (stem).
a) helical junctions
b) hairpin loop
c) bulge loop
d) interior loop
Explanation: The bulge loop refers to a single stranded region connecting two adjacent base-paired segments so that it “bubbles” out in the middle of a double helix on one side. The multi-branch loop is also called helical junctions.
10. The __________ refers to two single-stranded regions on opposite strands connecting two adjacent base-paired segments.
a) hairpin loop
b) interior loop
c) pseudoknot loop
d) helical junctions
Explanation: In addition to the traditional secondary structural elements, base pairing between loops of different secondary structural elements can result in a higher level of structures such as pseudoknots, kissing hairpins, and hairpin–bulge contact. A pseudoknot loop refers to base pairing formed between loop residues within a hairpin loop and residues outside the hairpin loop.