Q.1 What are the three components that make up a nucleotide in RNA?
A phosphate group, a deoxyribose sugar, and a nitrogenous base
A phosphate group, a ribose sugar, and a nitrogenous base
A phosphate group, a ribose sugar, and a methyl group
A phosphate group, a deoxyribose sugar, and a methyl group
Explanation - RNA nucleotides consist of a phosphate, a ribose (5‑carbon) sugar, and one of four nitrogenous bases (A, U, G, C).
Correct answer is: A phosphate group, a ribose sugar, and a nitrogenous base
Q.2 Which nitrogenous base is found in RNA but not in DNA?
Adenine
Guanine
Thymine
Uracil
Explanation - RNA contains uracil (U) instead of thymine (T), which is present in DNA.
Correct answer is: Uracil
Q.3 What type of RNA carries the genetic code from the nucleus to the ribosome?
tRNA
rRNA
mRNA
snRNA
Explanation - Messenger RNA (mRNA) is transcribed from DNA and transports the genetic information to ribosomes for protein synthesis.
Correct answer is: mRNA
Q.4 Which RNA molecule is primarily responsible for catalyzing peptide bond formation in the ribosome?
tRNA
mRNA
rRNA
miRNA
Explanation - Ribosomal RNA (rRNA) forms the core of the ribosome’s peptidyl transferase center, catalyzing peptide bond formation.
Correct answer is: rRNA
Q.5 What is the main structural feature of transfer RNA (tRNA) that allows it to recognize specific codons?
A double‑helix region
An anticodon loop
A poly‑A tail
A 5′ cap
Explanation - tRNA contains an anticodon loop that base‑pairs with the complementary mRNA codon during translation.
Correct answer is: An anticodon loop
Q.6 During transcription, which enzyme synthesizes a complementary RNA strand from a DNA template?
DNA polymerase
RNA polymerase
Ribosome
Ligase
Explanation - RNA polymerase reads the DNA template strand and adds ribonucleotides to form a new RNA molecule.
Correct answer is: RNA polymerase
Q.7 In eukaryotes, where does the majority of RNA processing (capping, splicing, polyadenylation) occur?
Cytoplasm
Mitochondria
Nucleus
Endoplasmic reticulum
Explanation - All primary RNA processing steps happen in the nucleus before the mature mRNA is exported to the cytoplasm.
Correct answer is: Nucleus
Q.8 Which of the following modifications is added to the 5′ end of eukaryotic mRNA?
Poly‑U tail
5′‑phosphate
5′‑cap (7‑methylguanosine)
5′‑hydroxyl group
Explanation - A 7‑methylguanosine cap is attached to the 5′ end of eukaryotic mRNA, protecting it from degradation and aiding translation.
Correct answer is: 5′‑cap (7‑methylguanosine)
Q.9 What is the function of a poly‑A tail on eukaryotic mRNA?
To initiate transcription
To signal termination of translation
To stabilize mRNA and facilitate nuclear export
To serve as a ribosome binding site
Explanation - The poly‑A tail protects mRNA from degradation, aids in export from the nucleus, and enhances translation efficiency.
Correct answer is: To stabilize mRNA and facilitate nuclear export
Q.10 Which RNA type is involved in the spliceosome complex to remove introns from pre‑mRNA?
tRNA
snRNA
rRNA
miRNA
Explanation - Small nuclear RNAs (snRNAs) combine with proteins to form snRNPs, the core components of the spliceosome.
Correct answer is: snRNA
Q.11 What is the typical length range of a microRNA (miRNA) molecule?
18‑25 nucleotides
30‑40 nucleotides
50‑70 nucleotides
100‑150 nucleotides
Explanation - MiRNAs are short, non‑coding RNAs of about 18‑25 nucleotides that regulate gene expression post‑transcriptionally.
Correct answer is: 18‑25 nucleotides
Q.12 Which of the following best describes a ribozyme?
An RNA molecule that can act as a catalyst
An RNA that encodes ribosomal proteins
A DNA‑RNA hybrid molecule
A protein that binds RNA
Explanation - Ribozymes are RNA molecules with catalytic activity, capable of speeding up biochemical reactions without proteins.
Correct answer is: An RNA molecule that can act as a catalyst
Q.13 In the secondary structure of RNA, which base‑pairing pattern is most common?
A‑C and G‑U
A‑U and G‑C
A‑G and C‑U
A‑T and G‑C
Explanation - RNA forms Watson‑Crick base pairs A‑U and G‑C; wobble G‑U pairs can also occur but are less common.
Correct answer is: A‑U and G‑C
Q.14 What is the primary structural motif formed by complementary base pairing within a single RNA strand?
Double helix
Hairpin loop (stem‑loop)
Z‑DNA
Triple helix
Explanation - Intra‑strand base pairing creates stem‑loop (hairpin) structures, a key element of RNA secondary structure.
Correct answer is: Hairpin loop (stem‑loop)
Q.15 Which type of RNA is most abundant in the cell and forms the structural and catalytic core of ribosomes?
tRNA
rRNA
mRNA
snRNA
Explanation - Ribosomal RNA makes up ~80% of total cellular RNA and is essential for ribosome structure and function.
Correct answer is: rRNA
Q.16 Which of the following best describes the role of small interfering RNA (siRNA) in cells?
Enhancing translation of target mRNA
Guiding the spliceosome to splice sites
Directing degradation of complementary mRNA
Serving as a primer for DNA synthesis
Explanation - siRNAs are incorporated into the RISC complex and mediate sequence‑specific mRNA cleavage, silencing gene expression.
Correct answer is: Directing degradation of complementary mRNA
Q.17 What is the significance of the ‘wobble’ position in the tRNA anticodon?
It determines the tRNA’s three‑dimensional shape
It allows for non‑standard base pairing with the third codon base
It is where the amino acid is attached
It caps the tRNA molecule
Explanation - The wobble position (first base of anticodon) can pair with multiple codon bases, providing flexibility in codon recognition.
Correct answer is: It allows for non‑standard base pairing with the third codon base
Q.18 Which viral genome type is composed solely of single‑stranded RNA that can act directly as mRNA?
Double‑stranded DNA virus
Double‑stranded RNA virus
Positive‑sense single‑stranded RNA virus
Negative‑sense single‑stranded RNA virus
Explanation - Positive‑sense ssRNA viruses have genomes that can be immediately translated by host ribosomes.
Correct answer is: Positive‑sense single‑stranded RNA virus
Q.19 In the context of RNA secondary structure prediction, what does the term “minimum free energy (MFE) structure” refer to?
The structure with the highest melting temperature
The most thermodynamically stable predicted folding
The structure with the greatest number of hairpins
The longest continuous double‑helix region
Explanation - MFE is the predicted RNA conformation with the lowest Gibbs free energy, representing the most stable structure under physiological conditions.
Correct answer is: The most thermodynamically stable predicted folding
Q.20 Which of the following statements about RNA editing is true?
It occurs only in prokaryotes
It changes the DNA sequence after transcription
It can alter nucleotides within an RNA molecule after transcription
It removes introns from pre‑mRNA
Explanation - RNA editing modifies nucleotide sequences of RNA transcripts (e.g., A‑to‑I editing) without altering the underlying DNA.
Correct answer is: It can alter nucleotides within an RNA molecule after transcription
Q.21 What structural element of ribosomal RNA is essential for the peptidyl transferase activity?
The A‑site loop
The P‑site stem
The 23S rRNA domain V (in bacteria)
The 5′‑UTR hairpin
Explanation - Domain V of bacterial 23S rRNA forms the catalytic center of the ribosome where peptide bond formation occurs.
Correct answer is: The 23S rRNA domain V (in bacteria)
Q.22 Which technique is most commonly used to determine the secondary structure of an RNA molecule experimentally?
X‑ray crystallography
Northern blotting
Selective 2′‑Hydroxyl Acylation analyzed by Primer Extension (SHAPE)
Western blotting
Explanation - SHAPE chemistry probes RNA flexibility, allowing inference of secondary structure through primer extension analysis.
Correct answer is: Selective 2′‑Hydroxyl Acylation analyzed by Primer Extension (SHAPE)
Q.23 In eukaryotic translation initiation, which factor binds the 5′‑cap of mRNA?
eIF4E
eIF2
eIF3
eIF5
Explanation - The cap‑binding protein eIF4E recognizes the 7‑methylguanosine cap and recruits the ribosome to the mRNA.
Correct answer is: eIF4E
Q.24 Which of the following best describes the function of a riboswitch?
A protein that binds DNA to regulate transcription
An RNA segment that changes conformation upon binding a metabolite to regulate gene expression
A DNA sequence that initiates replication
A membrane channel that transports ions
Explanation - Riboswitches are regulatory RNA elements that alter their structure upon ligand binding, influencing transcription or translation.
Correct answer is: An RNA segment that changes conformation upon binding a metabolite to regulate gene expression
Q.25 Which of the following is a characteristic of the RNA world hypothesis?
DNA was the first genetic material
Proteins were the first catalysts
RNA could have served both as genetic material and catalyst
Lipids formed the first cell membranes
Explanation - The RNA world hypothesis proposes that early life used RNA for both information storage and catalytic functions before DNA and proteins evolved.
Correct answer is: RNA could have served both as genetic material and catalyst
Q.26 What is the typical function of the 3′‑untranslated region (3′‑UTR) of an mRNA?
Coding for a peptide chain
Binding the ribosome’s P‑site
Regulating mRNA stability and localization
Initiating transcription
Explanation - The 3′‑UTR contains regulatory elements that affect mRNA half‑life, transport, and translation efficiency.
Correct answer is: Regulating mRNA stability and localization
Q.27 Which enzyme is responsible for adding the poly‑A tail to eukaryotic pre‑mRNA?
RNA polymerase II
Poly(A) polymerase
RNase H
Spliceosome
Explanation - Poly(A) polymerase catalyzes the addition of adenosine residues to the 3′ end of pre‑mRNA after cleavage.
Correct answer is: Poly(A) polymerase
Q.28 In the context of RNA tertiary structure, what is a pseudoknot?
A double‑helix formed by two RNA strands
A structure where bases in a loop pair with a region outside the stem‑loop
A protein‑RNA complex
A linear RNA segment with no secondary structure
Explanation - Pseudoknots involve base pairing between loop nucleotides and a distant sequence, creating a knot‑like tertiary fold.
Correct answer is: A structure where bases in a loop pair with a region outside the stem‑loop
Q.29 Which of the following RNAs is directly involved in the regulation of gene expression by targeting mRNA for degradation or translational repression?
tRNA
rRNA
miRNA
snRNA
Explanation - MicroRNAs (miRNAs) bind complementary sequences in target mRNAs, leading to translational repression or degradation.
Correct answer is: miRNA
Q.30 What is the main purpose of the Shine‑Dalgarno sequence in prokaryotic mRNA?
To serve as a termination signal
To bind the ribosomal 5S rRNA
To align the ribosome with the start codon
To encode a signal peptide
Explanation - The Shine‑Dalgarno sequence pairs with the 16S rRNA, positioning the ribosome for proper start codon recognition.
Correct answer is: To align the ribosome with the start codon
Q.31 Which RNA modification converts adenosine to inosine in pre‑tRNA?
Methylation
Deamination
Acetylation
Phosphorylation
Explanation - Adenosine deaminases acting on tRNA (ADAT) deaminate adenosine to inosine, expanding codon recognition.
Correct answer is: Deamination
Q.32 Which of the following is NOT a typical feature of ribosomal RNA genes in eukaryotes?
They are organized in tandem repeats
They contain introns that are spliced out
They are transcribed by RNA polymerase I
They are located in the nucleolus
Explanation - Eukaryotic rRNA genes are generally intron‑less; they are transcribed as a large precursor that is processed, not spliced.
Correct answer is: They contain introns that are spliced out
Q.33 During translation, which site on the ribosome holds the growing polypeptide chain?
A‑site
P‑site
E‑site
G‑site
Explanation - The peptidyl‑transferase (P) site contains the tRNA with the nascent peptide chain.
Correct answer is: P‑site
Q.34 What is the main difference between a ribosome‑bound tRNA in the A‑site and one in the P‑site?
A‑site tRNA carries the amino acid; P‑site tRNA carries the peptide
A‑site tRNA is uncharged; P‑site tRNA is charged
A‑site tRNA is attached to the ribosome via a protein; P‑site tRNA is not
A‑site tRNA binds the mRNA start codon; P‑site tRNA binds the stop codon
Explanation - The aminoacyl‑tRNA enters the A‑site; after peptide bond formation, the growing polypeptide is transferred to the tRNA in the P‑site.
Correct answer is: A‑site tRNA carries the amino acid; P‑site tRNA carries the peptide
Q.35 Which of the following best explains why RNA is more prone to hydrolysis than DNA?
RNA contains a 2′‑hydroxyl group on the ribose sugar
RNA has a double‑helix structure
RNA is single‑stranded
RNA lacks a phosphate backbone
Explanation - The 2′‑OH can act as a nucleophile, cleaving the phosphodiester bond, making RNA chemically less stable.
Correct answer is: RNA contains a 2′‑hydroxyl group on the ribose sugar
Q.36 Which of the following is a common method for quantifying specific RNA levels in a sample?
Southern blot
Northern blot
Western blot
Chromatin immunoprecipitation
Explanation - Northern blotting separates RNA by size and uses labeled probes to detect specific transcripts.
Correct answer is: Northern blot
Q.37 What is the primary role of the enzyme Dicer in RNA interference pathways?
Adding a poly‑A tail to mRNA
Cleaving double‑stranded RNA into siRNA fragments
Binding to the ribosome’s A‑site
Methylating rRNA
Explanation - Dicer processes long dsRNA into ~21‑nt siRNA duplexes that are loaded into the RISC complex.
Correct answer is: Cleaving double‑stranded RNA into siRNA fragments
Q.38 Which type of RNA is directly involved in the transport of amino acids to the ribosome?
mRNA
tRNA
rRNA
snRNA
Explanation - Transfer RNA (tRNA) carries specific amino acids to the ribosome during protein synthesis.
Correct answer is: tRNA
Q.39 In eukaryotes, which protein complex removes introns from pre‑mRNA?
Ribosome
Spliceosome
RNA polymerase II
RNA helicase
Explanation - The spliceosome, composed of snRNPs and proteins, catalyzes intron removal and exon ligation.
Correct answer is: Spliceosome
Q.40 Which of the following RNA species is typically involved in the innate immune response against viruses?
tRNA
rRNA
siRNA
snRNA
Explanation - siRNAs derived from viral dsRNA trigger antiviral RNAi pathways, degrading viral genomes.
Correct answer is: siRNA
Q.41 What structural feature distinguishes the large subunit of prokaryotic ribosomes from that of eukaryotic ribosomes?
Presence of 5S rRNA only in prokaryotes
Different rRNA composition (50S vs 60S)
Absence of proteins in the eukaryotic large subunit
Lack of a peptidyl‑transferase center in prokaryotes
Explanation - Prokaryotic large subunits are 50S (23S + 5S rRNA), while eukaryotic large subunits are 60S (28S, 5.8S, 5S rRNA).
Correct answer is: Different rRNA composition (50S vs 60S)
Q.42 Which RNA modification is most common in the anticodon loop of tRNA and is crucial for proper codon recognition?
5‑methylcytosine
Pseudouridine
Inosine
N6‑methyladenosine
Explanation - Inosine at the wobble position expands pairing capacity, allowing a single tRNA to recognize multiple codons.
Correct answer is: Inosine
Q.43 What is the typical outcome when a premature stop codon is encountered during translation?
The ribosome continues translation until the next start codon
The nascent peptide is released and translation terminates
The ribosome stalls permanently
The mRNA is immediately degraded
Explanation - Release factors recognize stop codons, catalyzing peptide release and ribosome disassembly.
Correct answer is: The nascent peptide is released and translation terminates
Q.44 Which of the following best describes the function of a ribosome‑binding site (RBS) in bacterial mRNA?
It signals the termination of transcription
It encodes the first amino acid of the protein
It aligns the ribosome for translation initiation
It recruits RNA polymerase
Explanation - The RBS (Shine‑Dalgarno sequence) base‑pairs with 16S rRNA, positioning the ribosome at the start codon.
Correct answer is: It aligns the ribosome for translation initiation
Q.45 Which of the following statements about RNA‑dependent RNA polymerase (RdRP) is correct?
It synthesizes DNA from an RNA template
It is found only in eukaryotes
It synthesizes RNA from an RNA template, often in viruses
It adds poly‑A tails to mRNA
Explanation - RdRP replicates RNA genomes of many RNA viruses by using RNA as a template.
Correct answer is: It synthesizes RNA from an RNA template, often in viruses
Q.46 What is the primary purpose of the 5′‑cap structure on eukaryotic mRNA?
To serve as a ribosome entry site
To signal mRNA degradation
To protect mRNA from exonucleases and aid translation initiation
To encode a signal peptide
Explanation - The 5′‑cap prevents degradation and is recognized by initiation factors for translation.
Correct answer is: To protect mRNA from exonucleases and aid translation initiation
Q.47 Which of the following RNA molecules can act as a template for protein synthesis?
tRNA
rRNA
mRNA
snRNA
Explanation - Messenger RNA carries codons that specify the amino acid sequence of a protein.
Correct answer is: mRNA
Q.48 In the context of RNA folding, what does the term “thermodynamic ensemble” refer to?
All possible RNA sequences of a given length
All secondary structures weighted by their Boltzmann probabilities
The collection of ribosomes in a cell
The set of all proteins translated from a single mRNA
Explanation - A thermodynamic ensemble includes all possible folds of an RNA, each assigned a probability based on its free energy.
Correct answer is: All secondary structures weighted by their Boltzmann probabilities
Q.49 Which RNA modification is most prevalent in eukaryotic mRNA and often occurs near stop codons?
5‑methylcytosine (m5C)
N6‑methyladenosine (m6A)
Pseudouridine (Ψ)
2′‑O‑methylation
Explanation - m6A is the most common internal modification of eukaryotic mRNA, influencing stability and translation.
Correct answer is: N6‑methyladenosine (m6A)
Q.50 Which of the following best explains why ribosomal RNA is highly conserved across species?
It does not participate in catalysis
Its sequence determines cell shape
Its structure is essential for ribosome function
It encodes proteins
Explanation - Conserved rRNA sequences maintain the structural and catalytic integrity of the ribosome, limiting permissible mutations.
Correct answer is: Its structure is essential for ribosome function
Q.51 What is the primary function of the 3′‑UTR of a viral RNA genome that lacks a poly‑A tail?
Encode viral structural proteins
Recruit host ribosomes for translation
Regulate genome replication and stability
Signal for viral RNA degradation
Explanation - In many RNA viruses, the 3′‑UTR contains elements required for replication, translation control, and protection from nucleases.
Correct answer is: Regulate genome replication and stability
Q.52 Which of the following is a characteristic of a hammerhead ribozyme?
It requires protein cofactors for activity
It catalyzes self‑cleavage of RNA
It binds DNA to initiate replication
It forms a double‑helix with DNA
Explanation - Hammerhead ribozymes are small RNA motifs that self‑cleave via intramolecular catalysis.
Correct answer is: It catalyzes self‑cleavage of RNA
Q.53 In bacteria, the termination of transcription is commonly mediated by which RNA structure?
Stem‑loop followed by poly‑U tract (rho‑independent)
5′‑cap structure
Poly‑A tail
Riboswitch
Explanation - Rho‑independent termination involves formation of a GC‑rich hairpin followed by a series of uracils, destabilizing the RNA‑DNA hybrid.
Correct answer is: Stem‑loop followed by poly‑U tract (rho‑independent)
Q.54 Which of the following RNAs is most directly involved in the process of RNA editing in the mitochondria of kinetoplastid protozoa?
gRNA (guide RNA)
snRNA
miRNA
tRNA
Explanation - Guide RNAs direct insertion and deletion of uridines during mitochondrial RNA editing in kinetoplastids.
Correct answer is: gRNA (guide RNA)
Q.55 What is the main purpose of the Kozak consensus sequence in eukaryotic mRNA?
Signal transcription termination
Facilitate ribosome binding and accurate start‑codon recognition
Promote poly‑A tail addition
Direct RNA splicing
Explanation - The Kozak sequence (gccRccAUGG) flanking the start codon enhances translation initiation efficiency.
Correct answer is: Facilitate ribosome binding and accurate start‑codon recognition
Q.56 Which of the following best describes the function of the enzyme RNase P?
It degrades mRNA in the cytoplasm
It cleaves the 5′ leader sequence from precursor tRNA
It adds a poly‑A tail to mRNA
It synthesizes rRNA
Explanation - RNase P is a ribonucleoprotein that processes the 5′ ends of pre‑tRNA molecules.
Correct answer is: It cleaves the 5′ leader sequence from precursor tRNA
Q.57 Which of the following RNA molecules is most directly involved in the regulation of the lac operon in E. coli?
mRNA
tRNA
sRNA (small regulatory RNA)
rRNA
Explanation - Small RNAs can bind to the lac mRNA to influence its stability and translation, modulating operon activity.
Correct answer is: sRNA (small regulatory RNA)
Q.58 What is the functional consequence of a mutation that disrupts a stem‑loop structure in the 5′‑UTR of an mRNA?
It always causes immediate mRNA degradation
It can alter translation efficiency by affecting ribosome scanning
It converts the mRNA into a tRNA
It has no effect on the mRNA
Explanation - Stem‑loops in the 5′‑UTR can impede or enhance ribosome access, thus influencing translation rates.
Correct answer is: It can alter translation efficiency by affecting ribosome scanning
Q.59 Which of the following is NOT a typical feature of a small nucleolar RNA (snoRNA)?
Guides chemical modifications of rRNA
Contains C/D or H/ACA box motifs
Acts as a template for DNA synthesis
Localizes to the nucleolus
Explanation - snoRNAs function in rRNA modification, not in DNA synthesis.
Correct answer is: Acts as a template for DNA synthesis
Q.60 Which RNA element is recognized by the protein complex eIF2 during translation initiation?
The poly‑A tail
The 5′‑cap
The start codon
The Shine‑Dalgarno sequence
Explanation - eIF2 bound to GTP delivers the initiator Met‑tRNAi to the start codon (AUG) in the P‑site.
Correct answer is: The start codon
Q.61 Which type of RNA is directly involved in the process of RNA‑directed DNA methylation (RdDM) in plants?
tRNA
rRNA
siRNA
miRNA
Explanation - Plant siRNAs guide the DNA methylation machinery to specific genomic loci, leading to transcriptional silencing.
Correct answer is: siRNA
Q.62 What is the main function of the protein complex called the Exosome in eukaryotic cells?
Synthesizing ribosomal proteins
Processing pre‑tRNA
Degrading and processing various RNA species
Adding 5′ caps to mRNA
Explanation - The exosome is a multi‑subunit complex that degrades defective or excess RNAs and processes certain RNAs.
Correct answer is: Degrading and processing various RNA species
Q.63 Which of the following best describes the term “RNA latency” in the context of retroviruses?
RNA is permanently integrated into the host genome
The viral RNA remains in the cytoplasm without being translated
The viral genome is stored as DNA and not expressed
The virus produces no RNA during infection
Explanation - Latency often refers to the presence of viral RNA (or proviral DNA) that is transcriptionally silent until reactivation.
Correct answer is: The viral RNA remains in the cytoplasm without being translated
Q.64 What is the primary reason that many RNA viruses have high mutation rates?
Their RNA polymerases lack proofreading activity
They replicate in the nucleus
They use DNA intermediates
Their genomes are double‑stranded
Explanation - RNA‑dependent RNA polymerases are error‑prone and lack 3′‑to‑5′ exonuclease proofreading, leading to rapid mutation.
Correct answer is: Their RNA polymerases lack proofreading activity
Q.65 Which of the following RNAs is directly involved in the formation of the spliceosome’s catalytic core?
U1 snRNA
U2 snRNA
U5 snRNA
U6 snRNA
Explanation - U6 snRNA forms part of the catalytic core together with U2, facilitating the transesterification reactions of splicing.
Correct answer is: U6 snRNA
Q.66 What is the effect of a point mutation that creates a premature stop codon in the coding region of an mRNA?
Production of a longer protein
Production of a truncated protein
Increased transcription of the gene
No effect on the protein product
Explanation - Premature termination results in a shortened polypeptide, often nonfunctional.
Correct answer is: Production of a truncated protein
Q.67 Which of the following best explains the role of the 3′‑terminal poly‑U tail found in some negative‑sense RNA viruses?
It serves as a ribosome binding site
It signals for RNA replication by the viral polymerase
It encodes a viral protein
It stabilizes the viral RNA in the host cell
Explanation - The poly‑U tail serves as a promoter element recognized by the viral RdRP to initiate replication.
Correct answer is: It signals for RNA replication by the viral polymerase
Q.68 Which of the following best describes an aptamer?
A protein that binds DNA
A short DNA or RNA molecule that binds a specific target with high affinity
A ribosomal subunit
A type of viral capsid protein
Explanation - Aptamers are nucleic acid ligands selected for tight binding to proteins, small molecules, or even cells.
Correct answer is: A short DNA or RNA molecule that binds a specific target with high affinity
Q.69 Which of the following is a key feature of the CRISPR‑Cas13 system compared to Cas9?
Cas13 targets DNA, while Cas9 targets RNA
Cas13 uses a guide RNA to bind and cleave single‑stranded RNA
Cas13 requires a PAM sequence
Cas13 integrates into the genome
Explanation - Cas13 is an RNA‑guided RNase that specifically targets RNA molecules for cleavage.
Correct answer is: Cas13 uses a guide RNA to bind and cleave single‑stranded RNA
Q.70 Which of the following best defines the term “RNA secondary structure”?
The linear sequence of nucleotides
The three‑dimensional folding of the RNA molecule
The pattern of intramolecular base pairing (e.g., stems, loops)
The interaction between RNA and proteins
Explanation - Secondary structure refers to base‑pairing interactions that generate stems, hairpins, bulges, and internal loops.
Correct answer is: The pattern of intramolecular base pairing (e.g., stems, loops)
Q.71 In the context of ribosome profiling, what does the technique primarily measure?
The rate of DNA replication
The location of ribosomes on mRNAs genome‑wide
The amount of RNA polymerase bound to promoters
The composition of the nucleolus
Explanation - Ribosome profiling (Ribo‑Seq) sequences ribosome‑protected mRNA fragments to map translation at nucleotide resolution.
Correct answer is: The location of ribosomes on mRNAs genome‑wide
Q.72 Which of the following RNA elements is essential for the proper termination of transcription in eukaryotes?
Poly‑A signal (AAUAAA)
TATA box
Kozak sequence
Shine‑Dalgarno sequence
Explanation - The poly‑A signal directs cleavage of the nascent transcript and addition of the poly‑A tail, marking the end of transcription.
Correct answer is: Poly‑A signal (AAUAAA)
Q.73 Which type of RNA is most directly involved in the process of RNA editing in the mitochondria of trypanosomes?
miRNA
gRNA
snRNA
tRNA
Explanation - Guide RNAs (gRNAs) direct the insertion and deletion of uridines during mitochondrial mRNA editing in trypanosomatids.
Correct answer is: gRNA
Q.74 What is the most common type of base pair that forms in the interior of an RNA hairpin stem?
A‑U and G‑C
A‑C and G‑U
A‑G and C‑U
A‑T and G‑C
Explanation - RNA hairpin stems are stabilized primarily by canonical Watson‑Crick pairs A‑U and G‑C, with occasional wobble G‑U pairs.
Correct answer is: A‑U and G‑C
Q.75 Which of the following statements about the “RNA world” hypothesis is FALSE?
RNA can store genetic information
RNA can have catalytic activity
DNA predates RNA in evolutionary history
RNA may have given rise to both DNA and proteins
Explanation - The RNA world hypothesis posits that RNA preceded DNA and proteins, not the other way around.
Correct answer is: DNA predates RNA in evolutionary history
Q.76 Which of the following RNA types is most directly associated with the regulation of alternative splicing?
tRNA
snRNA
rRNA
miRNA
Explanation - Small nuclear RNAs (snRNAs) are components of spliceosomal snRNPs that can influence splice site selection.
Correct answer is: snRNA
Q.77 In a ribosome, where is the peptidyl transferase activity physically located?
In a protein subunit of the small subunit
In the 23S rRNA of the large subunit
In the mRNA codon
In the tRNA anticodon loop
Explanation - The peptidyl transferase center is formed by the 23S rRNA (bacterial) or 28S rRNA (eukaryotic) within the large ribosomal subunit.
Correct answer is: In the 23S rRNA of the large subunit
Q.78 Which of the following is a key characteristic of the 5′‑cap structure on eukaryotic mRNA?
It is a triphosphate group attached directly to the first nucleotide
It consists of a 7‑methylguanosine linked via a 5′‑5′ triphosphate bridge
It is a poly‑U tail
It is a protein complex attached to the mRNA
Explanation - The 5′‑cap is a 7‑methylguanosine attached to the first nucleotide through a unique 5′‑5′ triphosphate linkage.
Correct answer is: It consists of a 7‑methylguanosine linked via a 5′‑5′ triphosphate bridge
Q.79 Which of the following best describes the function of the exosome complex in the nucleus?
Synthesizing ribosomal proteins
Processing pre‑rRNA
Degrading aberrant RNAs and processing certain stable RNAs
Adding a 5′‑cap to mRNA
Explanation - The nuclear exosome trims and degrades faulty RNAs and participates in the maturation of some RNAs.
Correct answer is: Degrading aberrant RNAs and processing certain stable RNAs
Q.80 What is the primary function of the RNA polymerase II C‑terminal domain (CTD) during transcription?
Catalyzing DNA synthesis
Recruiting RNA processing factors such as capping, splicing, and polyadenylation enzymes
Binding the ribosome
Providing the ATP for transcription
Explanation - The CTD of Pol II serves as a platform for the sequential recruitment of mRNA processing machinery.
Correct answer is: Recruiting RNA processing factors such as capping, splicing, and polyadenylation enzymes
Q.81 Which type of RNA is most commonly used as a therapeutic agent to silence disease‑related genes?
tRNA
rRNA
siRNA
snRNA
Explanation - Synthetic siRNAs can be introduced into cells to trigger RNAi‑mediated knockdown of target mRNAs.
Correct answer is: siRNA
Q.82 In the context of viral replication, what does the term "segmental genome" refer to?
A genome that is split into separate RNA molecules, each encoding different proteins
A genome that contains both DNA and RNA
A genome that is circular
A genome that is integrated into the host chromosome
Explanation - Segmented viruses (e.g., influenza) have genomes divided into multiple RNA segments.
Correct answer is: A genome that is split into separate RNA molecules, each encoding different proteins
Q.83 Which of the following best describes the function of the “ribosome profiling” technique?
Measuring RNA synthesis rates
Mapping the positions of ribosomes on mRNAs at nucleotide resolution
Identifying DNA‑binding proteins
Detecting RNA‑protein cross‑links
Explanation - Ribosome profiling (Ribo‑Seq) provides a snapshot of translating ribosomes across the transcriptome.
Correct answer is: Mapping the positions of ribosomes on mRNAs at nucleotide resolution
Q.84 Which RNA motif is commonly found at the 3′ end of many bacterial mRNAs and contributes to transcription termination?
Shine‑Dalgarno sequence
Rho‑binding site
Poly‑U tract following a stem‑loop
Kozak consensus
Explanation - Rho‑independent terminators consist of a GC‑rich hairpin followed by a stretch of uracils.
Correct answer is: Poly‑U tract following a stem‑loop
Q.85 Which of the following is a characteristic of the RNA component of telomerase?
It acts as a template for adding telomeric repeats
It encodes a protein that binds telomeres
It is a double‑stranded DNA segment
It functions as a ribosome
Explanation - The telomerase RNA provides the template for reverse transcription of telomeric DNA repeats.
Correct answer is: It acts as a template for adding telomeric repeats
Q.86 Which of the following best explains why certain RNA viruses have segmented genomes?
To increase mutation rates
To allow reassortment of gene segments during co‑infection, generating new strains
To avoid detection by the immune system
To enable DNA integration
Explanation - Segmented genomes facilitate genetic shuffling (reassortment) when multiple viruses infect the same cell, creating novel combinations.
Correct answer is: To allow reassortment of gene segments during co‑infection, generating new strains
Q.87 Which of the following RNA molecules directly guides the modification (e.g., methylation) of specific nucleotides in rRNA?
tRNA
snRNA
snoRNA
miRNA
Explanation - Small nucleolar RNAs (snoRNAs) base‑pair with rRNA to direct site‑specific chemical modifications.
Correct answer is: snoRNA
Q.88 What is the primary role of the 3′‑UTR in many viral RNAs that lack a poly‑A tail?
Encoding viral capsid proteins
Acting as a ribozyme for self‑cleavage
Regulating translation and replication via RNA secondary structures
Serving as a signal for nuclear export
Explanation - The 3′‑UTR of many RNA viruses contains elements essential for controlling translation efficiency and replication.
Correct answer is: Regulating translation and replication via RNA secondary structures
Q.89 Which of the following best describes the function of the RNA helicase activity of the eIF4A protein during translation initiation?
Adding a poly‑A tail to mRNA
Unwinding secondary structures in the 5′‑UTR to facilitate ribosome scanning
Cleaving the 5′ cap
Binding the start codon
Explanation - eIF4A is an ATP‑dependent helicase that resolves secondary structures in the 5′‑UTR, allowing the 43S complex to scan for the start codon.
Correct answer is: Unwinding secondary structures in the 5′‑UTR to facilitate ribosome scanning
Q.90 Which type of RNA is most commonly used as a molecular marker for phylogenetic studies due to its highly conserved nature?
tRNA
rRNA (especially 16S/18S)
miRNA
snRNA
Explanation - The 16S (prokaryotes) and 18S (eukaryotes) rRNA genes are highly conserved and widely used for constructing evolutionary relationships.
Correct answer is: rRNA (especially 16S/18S)
Q.91 In the context of RNA stability, which modification typically marks an mRNA for rapid degradation?
5′‑cap addition
Poly‑A tail shortening (deadenylation)
m6A methylation in the 5′‑UTR
Capping with a 5′‑triphosphate
Explanation - Deadenylation removes the protective poly‑A tail, leading to mRNA decay by exonucleases.
Correct answer is: Poly‑A tail shortening (deadenylation)
Q.92 Which RNA element functions as a molecular switch that changes conformation upon ligand binding to control gene expression?
Ribozyme
Riboswitch
siRNA
snRNA
Explanation - Riboswitches are regulatory RNA domains that alter their structure in response to specific metabolites, influencing transcription or translation.
Correct answer is: Riboswitch
Q.93 What is the primary chemical basis for the base‑pairing specificity in RNA?
Hydrogen bonding between complementary bases
Covalent bonds between nucleotides
Ionic interactions with metal ions
Van der Waals forces only
Explanation - Base pairing in RNA (A‑U, G‑C, and wobble G‑U) is governed by specific hydrogen bonds.
Correct answer is: Hydrogen bonding between complementary bases
Q.94 Which of the following best describes the role of the RNA polymerase II C‑terminal domain (CTD) phosphorylation cycle?
It directs the polymerase to the nuclear membrane
It coordinates the transition from transcription initiation to elongation and RNA processing
It degrades the newly formed RNA
It synthesizes the 5′‑cap structure
Explanation - Dynamic phosphorylation of the CTD regulates recruitment of factors needed for capping, splicing, and polyadenylation during transcription.
Correct answer is: It coordinates the transition from transcription initiation to elongation and RNA processing
Q.95 Which RNA‑binding protein complex is responsible for transporting mature mRNA from the nucleus to the cytoplasm?
Spliceosome
Exosome
TREX (transcription/export) complex
RISC
Explanation - The TREX complex couples transcription and mRNA processing with nuclear export via the nuclear pore.
Correct answer is: TREX (transcription/export) complex
Q.96 What is the primary advantage of using a ribozyme‑based therapeutic over traditional small‑molecule drugs?
Ribozymes can specifically cleave target RNA sequences
Ribozymes are more stable than proteins
Ribozymes can cross the blood‑brain barrier easily
Ribozymes do not require delivery systems
Explanation - Ribozymes can be engineered to recognize and catalytically cleave disease‑related RNAs with high specificity.
Correct answer is: Ribozymes can specifically cleave target RNA sequences
Q.97 Which of the following best describes the role of the “poly‑U tail” in certain negative‑sense RNA viruses?
It serves as a ribosome entry site
It acts as a promoter for viral polymerase during replication
It encodes a viral protein
It signals host cell apoptosis
Explanation - The poly‑U stretch at the 3′ end of negative‑sense genomes is recognized by the viral RNA‑dependent RNA polymerase to initiate replication.
Correct answer is: It acts as a promoter for viral polymerase during replication
Q.98 Which type of RNA is most commonly utilized in CRISPR‑Cas13 diagnostic platforms (e.g., SHERLOCK)?
Guide RNA (crRNA) that directs Cas13 to target RNA
tRNA for delivering amino acids
rRNA for ribosome assembly
snRNA for splicing
Explanation - Cas13 uses a CRISPR RNA (crRNA) to specifically bind and cleave target RNA sequences in diagnostic assays.
Correct answer is: Guide RNA (crRNA) that directs Cas13 to target RNA
Q.99 Which of the following best explains why ribosomal RNA is transcribed by RNA polymerase I in eukaryotes?
Pol I provides higher fidelity for protein‑coding genes
Pol I is specialized for high‑volume synthesis of rRNA
Pol I adds the 5′ cap to rRNA
Pol I processes rRNA introns
Explanation - RNA polymerase I is dedicated to producing large amounts of rRNA, a major component of ribosomes.
Correct answer is: Pol I is specialized for high‑volume synthesis of rRNA
Q.100 In the context of RNA secondary structure prediction, what does the term "base‑pairing probability" represent?
The likelihood that a given pair of nucleotides will form a hydrogen bond in the most stable structure
The frequency of a nucleotide in the genome
The probability that a sequence will be transcribed
The chance that RNA will be exported from the nucleus
Explanation - Base‑pairing probability is derived from the Boltzmann ensemble and indicates how often a specific pair appears across possible structures.
Correct answer is: The likelihood that a given pair of nucleotides will form a hydrogen bond in the most stable structure
Q.101 Which of the following RNA modifications is most frequently associated with enhancing translation efficiency?
m6A in the 5′‑UTR
Pseudouridine in the coding region
5′‑cap methylation
2′‑O‑methylation of the poly‑A tail
Explanation - N6‑methyladenosine (m6A) in the 5′‑UTR can recruit initiation factors and boost translation.
Correct answer is: m6A in the 5′‑UTR
Q.102 Which RNA species is primarily responsible for the recognition of splice donor and acceptor sites during pre‑mRNA splicing?
snRNA (U1 and U2)
tRNA
rRNA
miRNA
Explanation - U1 snRNA binds the 5′ splice site, while U2 snRNA pairs with the branch point sequence, initiating spliceosome assembly.
Correct answer is: snRNA (U1 and U2)
Q.103 What is the primary role of the ribosomal protein S12 in bacterial translation fidelity?
It catalyzes peptide bond formation
It interacts with the A‑site tRNA to ensure correct codon‑anticodon pairing
It binds the Shine‑Dalgarno sequence
It adds the poly‑A tail to mRNA
Explanation - S12 monitors the accuracy of tRNA selection at the A‑site, contributing to translational fidelity.
Correct answer is: It interacts with the A‑site tRNA to ensure correct codon‑anticodon pairing
Q.104 Which of the following best describes the function of the RNA‑dependent RNA polymerase (RdRP) in RNA interference pathways of some organisms?
Synthesizing double‑stranded RNA from single‑stranded RNA templates to amplify the silencing signal
Adding a poly‑A tail to siRNA
Transcribing DNA into RNA
Repairing damaged RNA molecules
Explanation - RdRPs generate secondary siRNAs, reinforcing RNAi responses in plants and some animals.
Correct answer is: Synthesizing double‑stranded RNA from single‑stranded RNA templates to amplify the silencing signal
Q.105 Which of the following RNA structures is most often targeted by the antiviral drug ribavirin?
tRNA anticodon loops
RNA G‑quadruplexes
RNA polymerase active site
Ribosomal RNA methylation sites
Explanation - Ribavirin is a nucleoside analog that inhibits viral RNA‑dependent RNA polymerases, disrupting replication.
Correct answer is: RNA polymerase active site
Q.106 What is the primary consequence of a mutation that abolishes the 5′‑cap on an eukaryotic mRNA?
Enhanced translation efficiency
Rapid degradation of the mRNA by exonucleases
Improved nuclear export
Increased poly‑A tail length
Explanation - The cap protects mRNA from 5′‑to‑3′ exonucleases and is required for efficient translation initiation.
Correct answer is: Rapid degradation of the mRNA by exonucleases
Q.107 Which of the following best explains why ribosomal RNA genes are present in multiple copies in eukaryotic genomes?
To increase genetic diversity
To meet the high demand for ribosome production
To encode different ribosomal proteins
To provide templates for tRNA synthesis
Explanation - High transcriptional output of rRNA necessitates multiple gene copies (rDNA repeats) for rapid ribosome biogenesis.
Correct answer is: To meet the high demand for ribosome production
Q.108 What is the primary purpose of the “ribosome‑binding site” (RBS) in bacterial mRNA?
To signal termination of translation
To recruit the ribosome for initiation of translation
To bind the poly‑A tail
To encode a signal peptide
Explanation - The RBS (Shine‑Dalgarno sequence) aligns the ribosome with the start codon for proper translation initiation.
Correct answer is: To recruit the ribosome for initiation of translation
Q.109 Which of the following is a hallmark of a functional ribozyme?
Dependence on a protein cofactor for activity
Ability to catalyze a chemical reaction without proteins
Requirement for a DNA template
Inability to fold into a defined secondary structure
Explanation - Ribozymes are RNA molecules with intrinsic catalytic activity, functioning independently of proteins.
Correct answer is: Ability to catalyze a chemical reaction without proteins
Q.110 Which of the following RNA elements can serve as a signal for nuclear export of mRNA?
5′‑cap
Exportin‑5 binding site
Nuclear export signal (NES) on proteins
TREX complex recruitment motifs
Explanation - TREX (Transcription/Export) complex binds to mRNA and interacts with nuclear pore components to mediate export.
Correct answer is: TREX complex recruitment motifs
Q.111 In the context of RNA virus replication, what is the function of a "cis‑acting element"?
A protein that enhances transcription
A region within the viral RNA that is required for replication or packaging
A host cell receptor
A ribosomal RNA subunit
Explanation - Cis‑acting elements are RNA sequences that function on the same molecule, essential for viral genome replication, translation, or encapsidation.
Correct answer is: A region within the viral RNA that is required for replication or packaging