1. What is RNA splicing?
A. Joining of DNA strands
B. Removal of introns and joining of exons
C. Addition of poly-A tail
D. Removal of exons and joining of introns
Answer: B
Explanation: RNA splicing involves removing non-coding introns and joining coding exons to form a functional mRNA molecule.
2. Which molecule plays a central role in RNA splicing?
A. DNA polymerase
B. Ribosome
C. Spliceosome
D. RNA helicase
Answer: C
Explanation: The spliceosome is a complex of proteins and RNA that catalyzes the removal of introns and the ligation of exons.
3. What sequences mark the splice sites in pre-mRNA?
A. Promoter and terminator
B. 5′ cap and poly-A tail
C. GU at 5′ and AG at 3′ splice sites
D. CA at 5′ and TG at 3′ splice sites
Answer: C
Explanation: Splice sites are defined by conserved sequences: GU at the 5′ end and AG at the 3′ end of the introns.
4. What is alternative splicing?
A. Adding multiple poly-A tails
B. Removal of exons instead of introns
C. Generating different mRNA molecules from the same pre-mRNA
D. Changing the sequence of exons
Answer: C
Explanation: Alternative splicing allows a single gene to produce multiple protein isoforms by rearranging the exons during RNA processing.
5. Which of the following is an example of alternative splicing?
A. Skipping of an exon
B. Inclusion of all introns
C. Circularization of RNA
D. Removal of exons and introns simultaneously
Answer: A
Explanation: Alternative splicing can result in exon skipping, where certain exons are excluded from the final mRNA.
6. The spliceosome consists of which RNA-protein complexes?
A. tRNA
B. snRNPs
C. miRNA
D. Ribozymes
Answer: B
Explanation: Small nuclear ribonucleoproteins (snRNPs) are the main components of the spliceosome.
7. What is the role of U1 snRNP in splicing?
A. Binds to the 3′ splice site
B. Binds to the branch point
C. Recognizes the 5′ splice site
D. Catalyzes exon joining
Answer: C
Explanation: U1 snRNP binds to the 5′ splice site and is essential for initiating the splicing process.
8. What is the branch point in splicing?
A. A conserved A residue in the intron
B. A junction between exons
C. The 5′ cap of mRNA
D. The poly-A tail
Answer: A
Explanation: The branch point is a conserved adenine (A) residue in the intron, crucial for lariat formation during splicing.
9. What is a lariat structure?
A. Circular DNA
B. Branched RNA intermediate in splicing
C. Linear DNA molecule
D. Complex protein structure
Answer: B
Explanation: During splicing, a lariat structure is formed when the 5′ end of an intron loops and attaches to the branch point.
10. Which diseases are linked to errors in splicing?
A. Diabetes and hypertension
B. Cystic fibrosis and spinal muscular atrophy
C. Alzheimer’s disease and malaria
D. Tuberculosis and cholera
Answer: B
Explanation: Defective splicing is implicated in diseases like cystic fibrosis and spinal muscular atrophy due to misprocessed mRNA.
11. How does alternative splicing contribute to protein diversity?
A. By mutating DNA sequences
B. By forming multiple mRNA variants
C. By degrading unused RNA
D. By preventing transcription
Answer: B
Explanation: Alternative splicing generates various mRNA isoforms from a single gene, leading to diverse protein products.
12. What is exon skipping?
A. Removal of introns
B. Inclusion of all exons
C. Skipping over certain exons during splicing
D. Rearranging exon sequences
Answer: C
Explanation: Exon skipping occurs when specific exons are omitted from the final mRNA sequence.
13. Which type of RNA modification is essential for splicing?
A. Polyadenylation
B. Methylation
C. Capping
D. Cleavage
Answer: C
Explanation: 5′ capping protects mRNA and facilitates recognition by the spliceosome for efficient splicing.
14. What regulates alternative splicing?
A. Promoter strength
B. Splicing factors like SR proteins
C. Ribosomal proteins
D. tRNA abundance
Answer: B
Explanation: Splicing factors such as SR proteins and hnRNPs regulate alternative splicing by influencing splice site selection.
15. What are splicing enhancers?
A. Sequences that recruit spliceosomes
B. Proteins that degrade RNA
C. Sites for ribosome binding
D. Non-functional sequences
Answer: A
Explanation: Splicing enhancers are RNA sequences that recruit splicing machinery to promote exon inclusion.
16. In which organisms is splicing most common?
A. Prokaryotes
B. Viruses
C. Eukaryotes
D. Archaea
Answer: C
Explanation: Splicing predominantly occurs in eukaryotic cells where introns are removed from pre-mRNA.
17. How is splicing experimentally studied?
A. Using CRISPR
B. RNA electrophoresis
C. Spliceosome assays
D. Polymerase chain reaction
Answer: C
Explanation: Spliceosome assays help analyze the splicing mechanism and the role of spliceosomal components.
18. What is trans-splicing?
A. Splicing between two exons in the same RNA
B. Splicing between exons from two different RNA molecules
C. Skipping over multiple exons
D. Simultaneous splicing of several RNAs
Answer: B
Explanation: Trans-splicing joins exons from different RNA molecules to create a functional transcript.
19. How do mutations in splice sites affect gene expression?
A. They always enhance expression
B. They can lead to loss of function or altered protein products
C. They have no effect
D. They always increase protein stability
Answer: B
Explanation: Mutations at splice sites can disrupt mRNA processing, leading to defective proteins or disease.
20. Which tool is used to predict splicing patterns?
A. BLAST
B. SpliceAid
C. Galaxy
D. RNAfold
Answer: B
Explanation: SpliceAid is a bioinformatics tool used to predict splicing regulators and patterns.
21. Which structure does U2 snRNP recognize?
A. The 5′ splice site
B. The branch point
C. The poly-A tail
D. The promoter region
Answer: B
Explanation: U2 snRNP binds to the branch point sequence and helps position the spliceosome for intron removal.
22. What are splicing silencers?
A. Regions that prevent splicing
B. Sequences that inhibit specific splice site use
C. Sites where splicing starts
D. Non-functional proteins
Answer: B
Explanation: Splicing silencers are RNA sequences that reduce the use of nearby splice sites, affecting exon inclusion.
23. What is the consequence of intron retention?
A. Functional proteins are produced
B. Degraded or non-functional mRNA
C. Enhanced transcription
D. Increased translation efficiency
Answer: B
Explanation: Introns retained in the mRNA may result in frameshift mutations or degradation of the transcript.
24. Which of the following is an outcome of alternative splicing?
A. mRNA degradation
B. Creation of multiple proteins from a single gene
C. DNA replication
D. RNA interference
Answer: B
Explanation: Alternative splicing allows one gene to produce various proteins by selecting different exon combinations.
25. What is exon shuffling?
A. Reordering of DNA sequences
B. Recombination of exons to create new genes
C. Translation of exons
D. Degradation of RNA
Answer: B
Explanation: Exon shuffling creates new genes by rearranging existing exons during evolution.
