RNA Structure MCQ

Question 1 : Which of the following is the smallest of the RNAs?

1. 1. Messenger RNA

   2. Transfer RNAs

   3. Ribosomal RNAs

   4. All of these

Answer : B

Explanation: tRNA is the smallest of the 3 types of RNA, possessing around 75-95 nucleotides. tRNAs are an essential component of translation, where their main function is the transfer of amino acids during protein synthesis. Therefore, they are called transfer RNAs.

Question 2 : The mRNA from which of the following would contain a poly-A tail?

1. 1. A restriction endonuclease from E. coli

   2. Bacterial alpha-amylase

   3. Human insulin

   4. Bacteriophage DNA ligase

Answer : C

Explanation:

Human insulin contains RNA which has a poly A tail in it. 

Question 3 : What is the average size (in bp) of a mature t-RNA?

1. 1. 80 bp

   2. 100 bp

   3. 120 bp

   4. 140 bp

Answer : A

Explanation: The T arm is a 4- to 5- bp stem ending in a loop containing the sequence TΨC where Ψ is pseudouridine, a modified uridine. Bases that have been modified, especially by methylation (e.g. by tRNA (guanine-N7-)-methyltransferase), occur in several positions throughout the tRNA.

Question 4 : What modified base is at the 5′ extremity of a capped eukaryotic m-RNA?

1. 1. 1-methyl-guanosine

   2. 1-methyl-adenosine

   3. 2′-O-methyl-guanosine

   4. 7-methyl-guanosine

Answer : D

Explanation:

In eukaryotes, the 5′ cap (cap-0), found on the 5′ end of an mRNA molecule, consists of a guanine nucleotide connected to mRNA via an unusual 5′ to 5′ triphosphate linkage. This guanosine is methylated on the 7 position directly after capping in vivo by a methyltransferase.

Question 5 : What is the function of messenger RNA?

1. 1. It carries amino acids

   2. It is a component of the ribosomes

   3. It is a direct copy of a gene

   4. It is the genetic material of some organisms

Answer : C

Explanation:

Specifically, messenger RNA (mRNA) carries the protein blueprint from a cell’s DNA to its ribosomes, which are the “machines” that drive protein synthesis. Transfer RNA (tRNA) then carries the appropriate amino acids into the ribosome for inclusion in the new protein.

Question 6 : Retroviruses replicate via __________ intermediate

1. 1. RNA

   2. DNA

   3. mRNA

   4. rDNA

Answer : B

Explanation:

Retroviruses replicate by converting the RNA genome into the DNA intermediate. Reverse transcription occurs inside nucleocapsids during entry and the resulting double-strand DNA becomes integrated into the chromosome (ie, provirus).

Question 7 : During RNA synthesis, the DNA template sequence 5’Tp Ap Gp Cp 3′ Would be transcribed to produce which of the following RNA sequence?

1. 1. 5′-Ap Tp Cp Gp-3′

   2. 5′-Gp Cp Up Ap-3′

   3. 5′-Gp Cp Tp Ap-3′

   4. 5′-Ap Up Cp Gp-3′

Answer : 2

Explanation:

Question 8 : RNA instability in alkaline solutions is due to

1. 1. adenine

   2. ribose

   3. uracil

   4. single strand nature

Answer : B

Explanation: RNA is typically single-stranded. Rather than deoxyribose, RNA is composed of ribose sugars. The hydroxyl group in it makes it more unstable compared to DNA as it is more prone to hydrolysis and degradation.

Question 9 : In RNA, uracil pairs with

1. 1. adenine

   2. cytosine

   3. thymine

   4. guanine

Answer : A

Explanation: During the synthesis of an RNA strand from a DNA template (transcription), uracil pairs only with adenine, and guanine pairs only with cytosine.

Question 10 : Two features of the tRNA molecule associated, in converting the triplet codon to an amino acid, are

1. 1. in the T Loop and D stem and loop

   2. in the anticodon loop and D stem loop

   3. in the anticodon loop and the 3′ CCA end

   4. none of the above

Answer : C

Explanation: The two features of the tRNA molecule which are associated in converting the triplet codon to an amino acid, is the anticodon sequence.

Question 11 : A nicked RNA molecule can be ligated by

1. 1. T4 RNA ligase

   2. DNA polymerase

   3. T4 DNA ligase

   4. all of these

Answer : C

Explanation: In molecular biology, DNA ligase is a specific type of enzyme, a ligase, (EC 6.5. 1.1) that facilitates the joining of DNA strands together by catalyzing the formation of a phosphodiester bond.

Question 12 : The tertiary structure of yeast tRNA

1. 1. involves extensive base stacking interactions

   2. resembles the 3-dimensional structure of other tRNAs

   3. is maintained mostly by non-Watson-Crick base pairing

   4. all of the above

Answer : D

Explanation: Yeast tRNAPhe is a paradigm for the study of tertiary structure in RNA: its crystal structure is well-established (1–3), and under comparable ionic conditions, the crystal and solution structures possess nearly identical anticodon–acceptor (mean) interstim angles (1, 4, 5).

Question 13 : Which of following RNA characteristically contains unusual purines and pyrimidines?

1. 1. rRNA

   2. nRNA

   3. mRNA

   4. tRNA

Answer : D

Explanation: Transfer RNA consists of both usual and unusual nitrogen bases. the unusual nitrogen bases protect the tRNA from dehydration such as pseudouridine and ribothymidine. Usual nitrogen bases help in translation.

Question 14 : The anticodon is a structure on

1. 1. rRNA

   2. ribosome

   3. mRNA

   4. tRNA

Answer : B

Explanation: An anticodon is a unit of three nucleotides corresponding to the three bases of an mRNA codon. Each tRNA has a distinct anticodon triplet sequence that can form 3 complementary base pairs to one or more codons for an amino acid.

Question 15 : The genetic material of retroviruses such as HIV is

1. 1. DNA

   2. RNA

   3. protein

   4. all of these

Answer : B

Explanation: HIV is a retrovirus, which means it carries single-stranded RNA as its genetic material rather than the double-stranded DNA human cells carry. Retroviruses also have the enzyme reverse transcriptase, which allows it to copy RNA into DNA and use that DNA “copy” to infect human, or host, cells.