Rucete ✏ AP Biology In a Nutshell
14. Transcription and Translation — Practice Questions 2
This chapter introduces the flow of genetic information from DNA to RNA to protein, emphasizing the roles of transcription and translation in gene expression.
Need a quick review?
📘 Go to the Concept Summary
(Multiple Choice — Click to Reveal Answer)
1. Which of the following accurately describes the role of a promoter in transcription?
(A) Encodes the first amino acid of a protein
(B) Provides the ribosome binding site on mRNA
(C) Serves as the binding site for RNA polymerase
(D) Translates mRNA into protein
Answer
(C) — Promoters are specific DNA sequences that signal where RNA polymerase should begin transcription.
2. Which type of RNA is directly involved in catalyzing the formation of peptide bonds between amino acids?
(A) mRNA
(B) tRNA
(C) rRNA
(D) snRNA
Answer
(C) — Ribosomal RNA (rRNA) is the catalytic component of the ribosome and acts as a ribozyme.
3. What happens immediately after a tRNA delivers its amino acid to the ribosome during elongation?
(A) It is degraded in the nucleus
(B) It forms a peptide bond and exits the ribosome
(C) It returns to the nucleus to be recharged
(D) It is replaced by RNA polymerase
Answer
(B) — After peptide bond formation, the tRNA releases its amino acid and exits the ribosome from the E site.
4. Which of the following explains why transcription and translation are coupled in prokaryotes but not in eukaryotes?
(A) Prokaryotes do not process mRNA
(B) Eukaryotes lack ribosomes
(C) Eukaryotes perform both processes in the cytoplasm
(D) Prokaryotes lack DNA polymerase
Answer
(A) — Prokaryotic mRNA does not require processing and both transcription and translation occur in the cytoplasm, allowing coupling.
5. Which DNA strand would RNA polymerase use as a template if the coding strand is 5′-ATGCGT-3′?
(A) 3′-ATGCGT-5′
(B) 5′-TACGCA-3′
(C) 3′-TACGCA-5′
(D) 3′-AUGCGU-5′
Answer
(C) — The template strand is the complement of the coding strand and is read in the 3′ to 5′ direction to synthesize mRNA in the 5′ to 3′ direction.
6. What is the name of the sequence in eukaryotic DNA where transcription factors bind to assist RNA polymerase binding?
(A) Start codon
(B) Splice site
(C) TATA box
(D) Poly-A tail
Answer
(C) — The TATA box is a conserved sequence in eukaryotic promoters that helps position RNA polymerase II.
7. Which RNA molecule contains the codons that determine the amino acid sequence of a protein?
(A) tRNA
(B) rRNA
(C) mRNA
(D) snRNA
Answer
(C) — Messenger RNA (mRNA) carries codons that are read by the ribosome to build proteins.
8. Which of the following occurs in the nucleus of a eukaryotic cell?
(A) Translation
(B) Transcription
(C) Polypeptide folding
(D) Ribosome assembly
Answer
(B) — Transcription and RNA processing occur in the nucleus before the mRNA exits to the cytoplasm.
9. Which codon acts as the universal start codon in protein synthesis?
(A) UGA
(B) UAA
(C) AUG
(D) GUA
Answer
(C) — AUG codes for methionine and serves as the initiation codon in nearly all organisms.
10. What happens to the introns in a eukaryotic pre-mRNA transcript?
(A) They are translated into protein
(B) They are spliced out during processing
(C) They are capped and exported
(D) They remain in mature mRNA
Answer
(B) — Introns are noncoding regions that are removed during RNA splicing.
11. What type of mutation leads to a premature stop codon?
(A) Missense
(B) Frameshift
(C) Nonsense
(D) Silent
Answer
(C) — Nonsense mutations introduce an early stop codon, truncating the protein.
12. What part of the ribosome binds to the mRNA first during translation initiation?
(A) A site
(B) Large subunit
(C) E site
(D) Small subunit
Answer
(D) — The small ribosomal subunit binds to the mRNA and locates the start codon before the large subunit joins.
13. What does each tRNA molecule carry to the ribosome?
(A) Codon
(B) DNA
(C) Amino acid
(D) Ribosome
Answer
(C) — Each tRNA carries a specific amino acid that corresponds to its anticodon.
14. What ensures that the correct amino acid is added during translation?
(A) The ribosome recognizes the codon
(B) The tRNA's anticodon pairs with the mRNA codon
(C) RNA polymerase proofreads the RNA
(D) The Golgi apparatus modifies it
Answer
(B) — Accurate base pairing between tRNA anticodons and mRNA codons ensures correct amino acid placement.
15. What is the effect of alternative splicing on gene expression?
(A) It silences gene expression
(B) It allows one gene to produce multiple proteins
(C) It degrades introns faster
(D) It prevents translation
Answer
(B) — By splicing exons in various combinations, cells can create diverse proteins from one gene.
16. Which molecule adds the poly-A tail to pre-mRNA?
(A) RNA polymerase
(B) DNA ligase
(C) Poly-A polymerase
(D) Reverse transcriptase
Answer
(C) — Poly-A polymerase adds adenine nucleotides to the 3′ end of mRNA to form the poly-A tail.
17. Which mRNA sequence is complementary to the DNA template strand 3′-TACGGA-5′?
(A) 3′-AUGCCU-5′
(B) 5′-AUGCCU-3′
(C) 3′-TACGGA-5′
(D) 5′-TACGGA-3′
Answer
(B) — Transcription produces an mRNA strand complementary and antiparallel to the template: 5′-AUGCCU-3′.
18. What event terminates translation in both prokaryotes and eukaryotes?
(A) A start codon is reached
(B) A ribosomal RNA signal
(C) A release factor binds a stop codon
(D) A poly-A tail forms
Answer
(C) — When the ribosome encounters a stop codon, a release factor terminates translation and releases the polypeptide.
19. What feature of the genetic code enables organisms to tolerate some mutations without changing protein function?
(A) Universal codon table
(B) Redundancy (degeneracy)
(C) RNA processing
(D) Translation proofreading
Answer
(B) — Redundancy in the code allows some codons to code for the same amino acid, minimizing mutation effects.
20. What is the primary role of mRNA in gene expression?
(A) Synthesizing DNA
(B) Carrying the amino acid to the ribosome
(C) Coding for a protein
(D) Assembling ribosomes
Answer
(C) — mRNA carries the genetic instructions from DNA to the ribosome for protein synthesis.
21. Which RNA type is made directly from the DNA template during transcription?
(A) tRNA
(B) rRNA
(C) mRNA
(D) snRNA
Answer
(C) — mRNA is synthesized directly from DNA and contains codons used in translation.
22. Which sequence acts as a signal for termination of transcription in prokaryotes?
(A) Poly-A signal
(B) Stop codon
(C) Terminator sequence
(D) TATA box
Answer
(C) — A terminator sequence in DNA signals RNA polymerase to stop transcription in prokaryotes.
23. Which of the following best describes the relationship between codons and amino acids?
(A) One codon can specify many amino acids
(B) One amino acid can be specified by multiple codons
(C) Codons are made of amino acids
(D) Amino acids code for nucleotides
Answer
(B) — Due to redundancy in the genetic code, several codons can specify the same amino acid.
24. Which enzyme links amino acids to their corresponding tRNAs?
(A) RNA polymerase
(B) Aminoacyl-tRNA synthetase
(C) Ribosome
(D) Peptidyl transferase
Answer
(B) — This enzyme "charges" tRNAs with the correct amino acid before translation.
25. Which of the following describes a key difference between transcription in prokaryotes and eukaryotes?
(A) Only prokaryotes use RNA polymerase
(B) Eukaryotes do not process RNA
(C) Transcription and translation are coupled in prokaryotes
(D) Prokaryotes use exons and introns
Answer
(C) — In prokaryotes, transcription and translation occur simultaneously due to the lack of a nucleus.
26. A mutation alters the anticodon region of a tRNA. Which outcome is most likely?
(A) Ribosome assembly will fail
(B) An incorrect amino acid may be added to the polypeptide
(C) Transcription will stop prematurely
(D) The mRNA will be degraded
Answer
(B) — A mutated anticodon could mismatch with the mRNA codon, resulting in the wrong amino acid being incorporated.
27. Why are polycistronic mRNA molecules found only in prokaryotes?
(A) Eukaryotes do not splice their RNA
(B) Only prokaryotes produce ribosomal RNA
(C) Prokaryotic operons allow multiple genes to be transcribed into one mRNA
(D) Prokaryotic ribosomes are more efficient
Answer
(C) — In prokaryotes, operons produce mRNA containing multiple coding sequences (polycistronic mRNA).
28. A mutation prevents the addition of the 5′ cap to mRNA in eukaryotes. Which result is most likely?
(A) RNA polymerase will be unable to bind
(B) Introns will not be removed
(C) The mRNA will not be exported from the nucleus
(D) DNA replication will fail
Answer
(C) — The 5′ cap is required for nuclear export and ribosome recognition.
29. Which mechanism allows multiple proteins to be generated from a single eukaryotic gene?
(A) DNA polymerase proofreading
(B) Alternative splicing
(C) Ribosome skipping
(D) Codon redundancy
Answer
(B) — Alternative splicing rearranges exons to produce different mRNAs from the same pre-mRNA transcript.
30. In a prokaryotic cell, what would happen if a mutation removed the Shine-Dalgarno sequence from mRNA?
(A) RNA polymerase would not bind
(B) Transcription would continue indefinitely
(C) Ribosome binding would be impaired
(D) tRNA charging would stop
Answer
(C) — The Shine-Dalgarno sequence helps prokaryotic ribosomes recognize the start site for translation.
31. Which of the following best explains why retroviruses use reverse transcriptase?
(A) To edit host RNA
(B) To transcribe viral RNA into viral protein
(C) To convert RNA into DNA for integration into host genome
(D) To amplify tRNA molecules for infection
Answer
(C) — Reverse transcriptase creates a DNA copy of viral RNA, which integrates into the host’s genome.
32. Why do frameshift mutations usually have more severe consequences than point mutations?
(A) They occur more frequently
(B) They affect mRNA export
(C) They alter the reading frame, changing all downstream amino acids
(D) They create silent mutations
Answer
(C) — Frameshifts change every codon after the mutation, often resulting in completely different and nonfunctional proteins.
33. What feature of rRNA allows it to function as a ribozyme?
Answer
(A) — rRNA has catalytic activity and folds into specific three-dimensional structures that catalyze peptide bond formation.
34. A stop codon appears prematurely in a coding sequence due to a mutation. What is this type of mutation called?
(A) Silent
(B) Missense
(C) Nonsense
(D) Splice site
Answer
(C) — Nonsense mutations introduce a premature stop codon, resulting in truncated proteins.
35. In translation, what event occurs immediately after a peptide bond forms between amino acids?
(A) The ribosome disassembles
(B) The ribosome shifts down the mRNA
(C) The tRNA exits the nucleus
(D) RNA polymerase resumes transcription
Answer
(B) — After peptide bond formation, the ribosome translocates to the next codon to continue elongation.
36. Explain how the universality of the genetic code supports the theory of common ancestry among organisms.
Answer
The genetic code is nearly identical across all organisms, suggesting that they evolved from a common ancestor that used the same coding system for translating genes into proteins.
37. Describe how a mutation in the splice site of an intron could affect the resulting protein.
Answer
If a splice site is mutated, the intron may not be properly removed, leading to inclusion of noncoding sequences in the mature mRNA and a potentially nonfunctional protein.
38. Predict what would happen if a eukaryotic cell lacked snRNPs (small nuclear ribonucleoproteins).
Answer
Splicing of introns would not occur efficiently, resulting in unprocessed pre-mRNA that may not be translated properly.
39. Justify why prokaryotic mRNAs typically do not undergo splicing.
Answer
Prokaryotic genes are continuous and lack introns, so their mRNA transcripts are already in a translatable form without needing splicing.
40. What is the significance of the A site on the ribosome during translation?
Answer
The A site (aminoacyl site) is where incoming tRNAs carrying amino acids bind and match with the codon on the mRNA.
41. Explain how the redundancy of the genetic code can protect against some mutations.
Answer
Redundancy means multiple codons can specify the same amino acid, so a mutation might not alter the resulting protein (silent mutation).
42. Why is the 5′ to 3′ direction of transcription important for RNA synthesis?
Answer
RNA polymerase can only add nucleotides to the 3′ end, so the RNA strand must be synthesized in a 5′ to 3′ direction for proper elongation.
43. Describe the role of release factors in terminating translation.
Answer
Release factors bind to the stop codon in the A site, triggering disassembly of the ribosome and release of the completed polypeptide chain.
44. What would happen if a mutation changed the sequence of a start codon in mRNA?
Answer
The ribosome may not initiate translation correctly, or it may fail to recognize the mRNA entirely, resulting in no protein being produced.
45. How do transcription factors contribute to gene regulation in eukaryotes?
Answer
Transcription factors bind to specific DNA sequences (e.g., enhancers or promoters) and help recruit RNA polymerase, influencing whether a gene is transcribed.
46. Why is it significant that RNA polymerase does not require a primer, unlike DNA polymerase?
Answer
RNA polymerase can initiate synthesis de novo, which allows transcription to begin directly at promoter regions without an existing strand.
47. Explain how base-pairing rules ensure accuracy during transcription.
Answer
RNA polymerase adds RNA nucleotides that are complementary to the DNA template strand, ensuring a precise RNA copy is made.
48. What structural feature of tRNA enables it to interact with both the mRNA and an amino acid?
Answer
tRNA has an anticodon loop that base pairs with mRNA codons and a 3′ acceptor stem where the corresponding amino acid is attached.
49. How could a mutation that affects the promoter region of a gene influence transcription?
Answer
If the promoter is altered, RNA polymerase may not recognize or bind to the gene, reducing or preventing transcription.
50. Describe how transcription and translation differ in location and timing between prokaryotes and eukaryotes.
Answer
In prokaryotes, both processes occur in the cytoplasm and can happen simultaneously. In eukaryotes, transcription occurs in the nucleus and translation in the cytoplasm, separated by RNA processing.