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TestMaster MCQs

RNA Types Questions

Home Science RNA Types
Q. Which type of RNA is most abundant in a cell?
mRNA
snRNA
tRNA
rRNA

Explanation:

Ribosomal RNA (rRNA) constitutes approximately 80% of total cellular RNA, reflecting its structural and catalytic role in ribosomes.

Q. Which RNA type carries genetic information from DNA to ribosomes?
rRNA
tRNA
mRNA
miRNA

Explanation:

Messenger RNA (mRNA) serves as the intermediary between DNA (in the nucleus) and ribosomes (in the cytoplasm) where protein synthesis occurs.

Q. Which RNA type delivers amino acids to the growing polypeptide chain?
mRNA
snRNA
rRNA
tRNA

Explanation:

Transfer RNA (tRNA) carries specific amino acids to the ribosome, matching its anticodon to the mRNA codon.

Q. Which RNA type is the smallest in size?
hnRNA
tRNA
mRNA
rRNA

Explanation:

tRNA molecules are typically 70–90 nucleotides long — the smallest of the three major classes of RNA. miRNAs are even smaller (~22 nt) but are classified separately as small regulatory RNAs.

Q. The cloverleaf-shaped secondary structure is characteristic of:
siRNA
rRNA
tRNA
mRNA

Explanation:

tRNA folds into a characteristic cloverleaf structure with four stems/loops (D loop, anticodon loop, TΨC loop, variable loop) and further compacts into an L-shape.

Q. The three nucleotides on tRNA that pair with the mRNA codon are called the:
Intron
Exon
Codon
Anticodon

Explanation:

The anticodon is a 3-nucleotide sequence in the anticodon loop of tRNA that base-pairs with the mRNA codon, ensuring the correct amino acid is added.

Q. The amino acid attachment site of a tRNA is at its:
5' phosphate end
Anticodon loop
3' CCA end
D loop

Explanation:

The 3' end of tRNA (with the sequence CCA) carries the amino acid, which is attached by an aminoacyl-tRNA synthetase via an ester bond.

Q. The enzyme that attaches an amino acid to its specific tRNA is:
Peptidyl transferase
Aminoacyl-tRNA synthetase
Ribonuclease
RNA polymerase

Explanation:

Aminoacyl-tRNA synthetases activate amino acids (using ATP) and attach them to their cognate tRNAs. Each amino acid has its own specific synthetase.

Q. Which tRNA modification is important for its function and stability?
Presence of a poly-A tail
Presence of introns in mature form
Presence of a 5' m7G cap
Presence of unusual modified bases like pseudouridine

Explanation:

Post-transcriptional modification produces many unusual bases in tRNA, including pseudouridine (Ψ) and dihydrouridine (D), which are essential for folding and codon-anticodon interactions.

Q. Ribosomal RNA (rRNA) functions primarily to:
Provide structural and catalytic components of ribosomes
Carry genetic information from DNA
Deliver amino acids to ribosomes
Regulate gene expression by degradation of mRNA

Explanation:

rRNA is a structural and catalytic component of ribosomes. It helps position mRNA and tRNA, and catalyzes peptide bond formation (peptidyl transferase activity).

Q. The catalytic activity of the ribosome (peptidyl transferase) is mediated by:
rRNA
mRNA
tRNA
Protein enzymes only

Explanation:

The ribosome is a ribozyme — its catalytic activity for peptide bond formation is catalyzed by the 23S rRNA (prokaryotes) or 28S rRNA (eukaryotes), not by a protein enzyme.

Q. Which RNA type is found in the nucleolus and helps process pre-rRNA?
piRNA
snoRNA
miRNA
siRNA

Explanation:

snoRNAs (small nucleolar RNAs) guide chemical modifications (methylation and pseudouridylation) of pre-rRNA in the nucleolus.

Q. The spliceosome contains which type of small RNA?
snoRNA
siRNA
miRNA
snRNA

Explanation:

snRNAs (small nuclear RNAs, e.g., U1, U2, U4, U5, U6) complexed with proteins form snRNPs — the core components of the spliceosome.

Q. MicroRNAs (miRNAs) function primarily to:
Regulate gene expression by targeting mRNAs for translational repression or degradation
Carry amino acids to ribosomes
Synthesize rRNA in the nucleolus
Form the spliceosome

Explanation:

miRNAs are ~22 nt regulatory RNAs that base-pair with target mRNAs to inhibit translation or promote mRNA degradation, thereby controlling gene expression.

Q. Small interfering RNAs (siRNAs) differ from miRNAs mainly in that siRNAs:
Are found only in bacteria
Are longer than miRNAs
Typically pair with full complementarity to targets and direct cleavage
Are translated into proteins

Explanation:

siRNAs are typically derived from exogenous dsRNA or long hairpins and pair fully with their target mRNA to direct its cleavage. miRNAs are encoded in the genome and usually pair only partially with targets.

Q. Long non-coding RNAs (lncRNAs) are defined by being:
More than 200 nucleotides in length with no protein-coding potential
Translated into small peptides only
Shorter than 50 nucleotides
Found only in mitochondria

Explanation:

lncRNAs are >200 nt in length, lack coding potential, and regulate gene expression at transcriptional and post-transcriptional levels (e.g., Xist, HOTAIR).

Q. Xist RNA is an example of a lncRNA that functions in:
tRNA processing
Ribosome assembly
Histone mRNA stabilization
X-chromosome inactivation in female mammals

Explanation:

Xist (X-inactive specific transcript) coats the X chromosome from which it is transcribed and recruits silencing factors, resulting in X-chromosome inactivation in female mammals.

Q. Heterogeneous nuclear RNA (hnRNA) is:
Encoded by mitochondrial genes only
Only found in prokaryotes
The primary transcript that becomes mRNA after processing
The same as mature mRNA

Explanation:

hnRNA refers to the primary RNA polymerase II transcripts in the nucleus, which include both introns and exons and are processed into mature mRNA.

Q. The 5S rRNA is transcribed by which polymerase in eukaryotes?
RNA polymerase II
RNA polymerase I
RNA polymerase IV
RNA polymerase III

Explanation:

Unlike the other rRNAs (transcribed by RNA polymerase I), 5S rRNA is transcribed by RNA polymerase III in the nucleoplasm and then transported to the nucleolus for ribosome assembly.

Q. In bacteria, the 16S rRNA is part of which ribosomal subunit?
30S small subunit
50S large subunit
70S whole ribosome only
Both subunits equally

Explanation:

Bacterial ribosomes (70S) consist of a 30S subunit containing 16S rRNA and a 50S subunit containing 23S and 5S rRNAs. The 16S rRNA plays a key role in mRNA recognition.

Q. The Shine-Dalgarno sequence in bacterial mRNA is recognized by:
tRNA
The 5' cap of mRNA
The sigma factor
16S rRNA of the small ribosomal subunit

Explanation:

The Shine-Dalgarno (ribosome-binding site) is a purine-rich sequence upstream of the start codon that base-pairs with the anti-SD sequence in 16S rRNA, positioning the ribosome for initiation.

Q. Which of the following is NOT a type of RNA?
DNA
tRNA
rRNA
mRNA

Explanation:

DNA is a distinct nucleic acid. mRNA, tRNA, and rRNA are all types of RNA that function in gene expression.

Q. piRNAs (piwi-interacting RNAs) primarily function to:
Translate mRNA into protein
Form ribosomes
Add poly-A tails to mRNA
Silence transposons in germ cells

Explanation:

piRNAs silence transposons in the germline, protecting genome integrity from mobile genetic element mobilization.

Q. Which RNA component of telomerase serves as the template for telomere extension?
mRNA
tRNA
snRNA
TERC (telomerase RNA component)

Explanation:

Telomerase contains a catalytic reverse transcriptase protein (TERT) and an RNA component (TERC) that provides the template for synthesizing telomeric repeats.

Q. The half-life of a typical bacterial mRNA is:
Several days
24 hours
Indefinite (no degradation)
A few minutes

Explanation:

Bacterial mRNAs have very short half-lives — typically only a few minutes — allowing rapid responses to changing environmental conditions.

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