Transcription and RNA Processing Practice Questions
20 free Transcription and RNA Processing practice questions for the Zoology. Tap an option to answer — you get instant feedback, the correct answer, and a detailed explanation for every question.
Which eukaryotic RNA polymerase is specifically responsible for the transcription of protein-coding genes into pre-mRNA?
- A RNA polymerase I
- B RNA polymerase II
- C RNA polymerase III
- D RNA polymerase IV
Correct answer: RNA polymerase II
RNA polymerase II transcribes all protein-coding genes to produce mRNA. It also transcribes some small nuclear RNAs (snRNAs) and microRNAs, distinguishing it from Polymerase I (rRNA) and III (tRNA).
The 'TATA box' is a conserved promoter element in eukaryotes. What is its primary function during transcription initiation?
- A It serves as the binding site for the sigma factor in prokaryotes
- B It acts as a transcription termination signal for RNA polymerase
- C It recruits TATA-binding protein to position the pre-initiation complex
- D It is the site where the poly-A tail is added post-transcriptionally
Correct answer: It recruits TATA-binding protein to position the pre-initiation complex
The TATA box is located approximately 25-30 base pairs upstream of the transcription start site. It is recognized by the TATA-binding protein (TBP), a subunit of TFIID, which coordinates assembly of the pre-initiation complex at the promoter.
During transcription, the RNA molecule is synthesized in which direction?
- A 3' to 5' using the template strand read in the 5' to 3' direction
- B 5' to 3' using the coding strand read in the 3' to 5' direction
- C 5' to 3' using the template strand read in the 3' to 5' direction
- D 3' to 5' using the coding strand read in the 3' to 5' direction
Correct answer: 5' to 3' using the template strand read in the 3' to 5' direction
RNA polymerase adds nucleotides to the 3'-OH end of the growing RNA chain, making the synthesis direction 5' to 3'. To maintain complementarity, the enzyme must move along the template DNA strand in the 3' to 5' direction.
In prokaryotes, which subunit of the RNA polymerase holoenzyme is essential for promoter recognition and initiation specificity?
- A Alpha subunit
- B Sigma factor
- C Beta subunit
- D Omega subunit
Correct answer: Sigma factor
The sigma factor confers promoter specificity on RNA polymerase, guiding it to bind the -10 and -35 consensus sequences. After transcription initiation and synthesis of a short RNA, the sigma factor is released from the core enzyme.
Which unique chemical linkage characterizes the 5' cap added to eukaryotic mRNA?
- A 3'-5' phosphodiester bond
- B 5'-5' triphosphate bridge
- C 2'-5' phosphodiester bond
- D Covalent disulfide bridge
Correct answer: 5'-5' triphosphate bridge
The 5' cap consists of a 7-methylguanosine residue joined to the 5' end of the mRNA via an unusual 5'-5' triphosphate link. This structure protects the transcript from exonuclease degradation and aids in ribosome binding.
What is the primary role of the polyadenylation signal (AAUAAA) in eukaryotic transcripts?
- A It marks the transcription start site of the first exon
- B It directs cleavage and addition of the poly-A tail
- C It serves as the spliceosome assembly site
- D It initiates nuclear export of the mature mRNA
Correct answer: It directs cleavage and addition of the poly-A tail
The AAUAAA polyadenylation signal is recognized by cleavage and polyadenylation specificity factor (CPSF), which cleaves the transcript 10-30 nucleotides downstream. Poly-A Polymerase then adds ~200 adenine residues to the 3' end, stabilizing the mRNA.
RNA splicing involves the removal of non-coding sequences called _______ and the joining of coding sequences called _______.
- A Exons; Introns
- B Introns; Exons
- C Promoters; Enhancers
- D Codons; Anticodons
Correct answer: Introns; Exons
Introns are non-coding intervening sequences removed from the pre-mRNA during splicing. Exons are the expressed coding sequences that are ligated together to form the mature mRNA ready for translation.
The 'Lariat' structure is a transient intermediate formed during which molecular process?
- A DNA replication
- B Post-translational protein folding
- C Pre-mRNA splicing
- D 5' cap addition
Correct answer: Pre-mRNA splicing
During splicing, the 2'-OH of the branch-point adenine attacks the 5' splice site, forming a lariat intermediate in which the intron loops back on itself. This lariat is released and degraded after the exons are ligated.
Which small nuclear ribonucleoproteins (snRNPs) are the primary components of the spliceosome?
- A U1, U2, U4, U5, and U6
- B S1, S2, S3, S4, and S5
- C Rho, Tau, and NusB factors
- D TFIIA, TFIIB, and TFIID
Correct answer: U1, U2, U4, U5, and U6
The spliceosome is assembled from five snRNPs: U1, U2, U4, U5, and U6. These snRNPs recognize the 5' splice site, branch point, and 3' splice site to coordinate the two transesterification reactions of pre-mRNA splicing.
Alternative splicing is a mechanism that allows for which of the following?
- A Increased rate of chromosomal DNA replication
- B Multiple protein isoforms from one gene
- C Reverse transcription of RNA back to DNA
- D Correction of point mutations within coding exons
Correct answer: Multiple protein isoforms from one gene
Alternative splicing selectively includes or excludes different exons from the same pre-mRNA. A single gene can thereby produce multiple distinct protein isoforms, greatly expanding the proteome beyond what gene number alone would predict.
In prokaryotes, Rho-independent termination is characterized by the formation of what in the nascent RNA?
- A A poly-A tail added to the 3' end
- B A GC-rich hairpin followed by a U-rich stretch
- C A 7-methylguanosine cap on the transcript
- D A lariat loop in the nascent intron
Correct answer: A GC-rich hairpin followed by a U-rich stretch
Rho-independent (intrinsic) termination involves a GC-rich palindromic sequence that folds into a hairpin in the nascent RNA, stalling RNA polymerase. The downstream A-U base pairs in the DNA-RNA hybrid are then too weak to hold the transcript, causing dissociation.
Which enzyme complex carries out the process of RNA editing, such as the C-to-U conversion in apolipoprotein B mRNA?
- A Spliceosome
- B Deaminase enzymes
- C RNA polymerase II
- D Aminoacyl-tRNA synthetase
Correct answer: Deaminase enzymes
RNA editing involves the chemical modification of specific bases after transcription. For example, cytidine deaminase can convert cytosine to uracil, creating a premature stop codon that results in a shorter version of the protein in specific tissues.
Which of the following describes the function of the CTD (C-terminal domain) of RNA polymerase II?
- A It acts as a helicase to unwind the DNA duplex
- B It coordinates RNA processing by recruiting capping and splicing factors
- C It binds directly to the TATA box sequence
- D It catalyzes phosphodiester bond formation during elongation
Correct answer: It coordinates RNA processing by recruiting capping and splicing factors
The CTD of RNA Pol II contains multiple heptapeptide repeats (YSPTSPS) that are progressively phosphorylated during transcription. Phosphorylated CTD acts as a scaffold to recruit 5' capping enzymes, splicing factors, and 3' processing machinery, coupling transcription with mRNA processing.
What is the biological significance of mRNA capping?
- A It marks the site where transcription terminates
- B It retains the mRNA within the nucleus for processing
- C It protects mRNA and promotes ribosome recognition
- D It is required for initiating chromosomal DNA replication
Correct answer: It protects mRNA and promotes ribosome recognition
The 5' 7-methylguanosine cap protects mRNA from exonuclease degradation and is recognized by the Cap-Binding Complex (CBC) in the nucleus and eIF4E in the cytoplasm. This cap is essential for efficient ribosome binding and translation initiation.
A mutation in the branch point adenine of an intron would most likely result in:
- A Complete failure to initiate transcription upstream
- B Defective lariat formation and splicing arrest
- C Loss of the protective 5' cap structure
- D Failure of RNA polymerase to reach the terminator
Correct answer: Defective lariat formation and splicing arrest
The branch-point adenine provides the 2'-OH nucleophile for the first transesterification reaction of splicing. A mutation at this site prevents lariat formation, blocking the entire splicing pathway and leading to intron retention in the mature transcript.
Which statement regarding the 'coding strand' of DNA is correct?
- A It is used as the direct template by RNA polymerase
- B Its sequence matches the mRNA, with U in place of T
- C It is read by RNA polymerase in the 3' to 5' direction
- D It is also called the antisense or template strand
Correct answer: Its sequence matches the mRNA, with U in place of T
The coding (sense) strand is complementary to the template strand. Because RNA is synthesized complementary to the template, its sequence matches the coding strand — with uracil substituted for thymine. The coding strand is not directly used by RNA polymerase.
Post-transcriptional modifications are unique to eukaryotes because:
- A Prokaryotes lack RNA polymerase entirely
- B Prokaryotic transcription and translation are coupled
- C Prokaryotic genes contain no adenine nucleotides
- D Prokaryotes have no ribosomes for translation
Correct answer: Prokaryotic transcription and translation are coupled
In prokaryotes, the absence of a nuclear envelope means ribosomes can attach to and translate mRNA while it is still being transcribed — a process called coupled transcription-translation. This leaves no opportunity for the extensive post-transcriptional processing (capping, splicing, polyadenylation) seen in eukaryotes.
What is the function of TFIIH in the eukaryotic transcription pre-initiation complex?
- A It adds the 5' methyl cap to the nascent transcript
- B It has helicase activity to unwind DNA and kinase activity to phosphorylate the CTD
- C It recognizes and binds the TATA box sequence
- D It catalyzes the formation and addition of the poly-A tail
Correct answer: It has helicase activity to unwind DNA and kinase activity to phosphorylate the CTD
TFIIH is a multi-subunit general transcription factor. Its helicase activity creates the transcription bubble, while its kinase activity phosphorylates the RNA polymerase II CTD to trigger promoter clearance and the elongation phase.
Which molecules facilitate the export of mature mRNA from the nucleus to the cytoplasm?
- A Importins and the nuclear lamina complex
- B Exportins and the nuclear pore complex
- C DNA polymerase and associated repair factors
- D Sigma factors and core RNA polymerase
Correct answer: Exportins and the nuclear pore complex
Only fully processed, mature mRNA associated with specific export proteins (like TAP/NXF1) is permitted to pass through the nuclear pore complex. This serves as a quality control mechanism to ensure defective transcripts are not translated.
The 'Pribnow Box' is a sequence equivalent to which eukaryotic element?
- A Polyadenylation signal (AATAAA)
- B TATA box sequence
- C 5' splice site consensus
- D Upstream enhancer element
Correct answer: TATA box sequence
The Pribnow box is the -10 consensus sequence (TATAAT) in prokaryotic promoters. It serves a similar role to the eukaryotic TATA box by facilitating the initial unwinding of the DNA double helix.