Introduction: This quiz collection on RNA processing, splicing, editing and RNA amplification mechanisms is tailored for M.Pharm students studying Microbial and Cellular Biology (MPB102T). It emphasizes mechanistic understanding of eukaryotic and prokaryotic RNA maturation—mRNA capping, 3′ polyadenylation, spliceosome assembly, and intron classes—plus RNA editing systems such as ADAR and APOBEC, guide RNA–mediated editing in trypanosomes, and RNA amplification via RNA-dependent RNA polymerases and rolling-circle mechanisms. Questions focus on enzyme complexes (CPSF, CstF, PAP), snRNP functions, regulatory cis-elements (ESE/ESS), and consequences for translation and decay (EJC, NMD). These targeted MCQs reinforce concepts essential for pharmaceutical applications including drug targeting and gene-expression modulation.
Q1. What is the canonical sequence in pre-mRNA that signals cleavage and polyadenylation in most eukaryotic mRNAs?
- 5′-GCCGCC-3′
- 5′-AAUAAA-3′
- 5′-GU-3′
- 5′-AUG-3′
Correct Answer: 5′-AAUAAA-3′
Q2. Which complex binds the 5′ cap of newly synthesized eukaryotic mRNA to facilitate export and translation initiation?
- Exon junction complex (EJC)
- Cap-binding complex (CBC)
- Cleavage and polyadenylation specificity factor (CPSF)
- RNA-induced silencing complex (RISC)
Correct Answer: Cap-binding complex (CBC)
Q3. Which small nuclear ribonucleoprotein recognizes the 5′ splice site during early spliceosome assembly?
- U2 snRNP
- U5 snRNP
- U1 snRNP
- U4/U6 di-snRNP
Correct Answer: U1 snRNP
Q4. Group II introns that self-splice use a mechanism most similar to which cellular process in eukaryotes?
- Ribosomal translation
- Spliceosome-mediated pre-mRNA splicing
- RNA interference (RNAi)
- Polyadenylation
Correct Answer: Spliceosome-mediated pre-mRNA splicing
Q5. Which of the following proteins is a core component of the cleavage complex that recognizes the AAUAAA signal for polyadenylation?
- Poly(A) polymerase (PAP)
- CstF-64
- Cleavage and polyadenylation specificity factor (CPSF)
- hnRNP A1
Correct Answer: Cleavage and polyadenylation specificity factor (CPSF)
Q6. RNA editing by adenosine deaminases acting on RNA (ADARs) converts which nucleotide to which other nucleotide?
- Cytidine (C) to Uridine (U)
- Adenosine (A) to Inosine (I)
- Guanosine (G) to Adenosine (A)
- Uridine (U) to Cytidine (C)
Correct Answer: Adenosine (A) to Inosine (I)
Q7. The conserved dinucleotide sequences at the 5′ and 3′ ends of most spliceosomal introns are:
- 5′-GU and 3′-AG
- 5′-AC and 3′-GT
- 5′-AA and 3′-UU
- 5′-CU and 3′-GA
Correct Answer: 5′-GU and 3′-AG
Q8. Which factor is primarily responsible for adding the poly(A) tail to cleaved pre-mRNA?
- Poly(A) polymerase (PAP)
- CPSF
- CstF
- U1 snRNP
Correct Answer: Poly(A) polymerase (PAP)
Q9. Alternative splicing regulators that typically promote exon inclusion belong to which protein family?
- hnRNP family
- SR (serine/arginine-rich) proteins
- RISC-associated Argonautes
- Poly(A)-binding proteins (PABP)
Correct Answer: SR (serine/arginine-rich) proteins
Q10. In trypanosome mitochondrial RNA editing, guide RNAs direct insertion/deletion of which nucleotide?
- Adenosine (A)
- Cytidine (C)
- Guanosine (G)
- Uridine (U)
Correct Answer: Uridine (U)
Q11. The exon junction complex (EJC) is deposited at a defined position relative to exon–exon junctions and influences which mRNA quality-control pathway?
- RNA editing
- Nonsense-mediated decay (NMD)
- MicroRNA maturation
- Ribosomal frameshifting
Correct Answer: Nonsense-mediated decay (NMD)
Q12. Which snRNP pair forms a stable di-snRNP prior to assembly into the active spliceosome?
- U2 and U5
- U1 and U2
- U4 and U6
- U5 and U6
Correct Answer: U4 and U6
Q13. APOBEC1-mediated RNA editing in mammals modifies apolipoprotein B mRNA by converting which nucleotide to which, producing a truncated protein form?
- Adenosine (A) to Inosine (I)
- Cytidine (C) to Uridine (U)
- Guanosine (G) to Adenosine (A)
- Uridine (U) to Cytidine (C)
Correct Answer: Cytidine (C) to Uridine (U)
Q14. Which enzyme removes the 5′ cap during normal mRNA decay to promote exonucleolytic degradation?
- Dcp1/Dcp2 decapping complex
- Poly(A) polymerase
- RNase H
- Spliceosome
Correct Answer: Dcp1/Dcp2 decapping complex
Q15. RNA-dependent RNA polymerase (RdRP) activity in plants and some organisms is important for:
- Generating cDNA from mRNA for retrotransposition
- Amplifying small interfering RNA (siRNA) signals
- Cap formation on nascent transcripts
- Cleavage of group I introns
Correct Answer: Amplifying small interfering RNA (siRNA) signals
Q16. Which sequence element within an exon enhances splice site recognition by recruiting SR proteins?
- Exonic splicing enhancer (ESE)
- Exonic splicing silencer (ESS)
- Intronic branch point
- Polyadenylation signal
Correct Answer: Exonic splicing enhancer (ESE)
Q17. The lariat structure formed during splicing involves a 2′-5′ phosphodiester bond between the branch point adenosine and which nucleotide at the 5′ splice site?
- Last nucleotide of upstream exon
- Guanosine of the 5′ splice site
- Uridine adjacent to the 3′ splice site
- First nucleotide of the intron
Correct Answer: First nucleotide of the intron
Q18. Minor (U12-type) spliceosomes recognize introns with variant splice site consensus sequences; which snRNP is unique to the minor spliceosome?
- U2 snRNP
- U11 snRNP
- U5 snRNP
- U1 snRNP
Correct Answer: U11 snRNP
Q19. Rolling-circle RNA replication is used by some viroids and viral satellites; the mechanism primarily produces which type of intermediate?
- Linear single-copy RNA only
- Concatenated multimeric RNA copies
- Double-stranded DNA
- Circular double-stranded RNA
Correct Answer: Concatenated multimeric RNA copies
Q20. Which enzyme catalyzes the removal of the lariat intron after splicing to allow its turnover?
- Lariat debranching enzyme (DBR1)
- RNase P
- Poly(A) polymerase
- ADAR
Correct Answer: Lariat debranching enzyme (DBR1)
