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Chapter 12 Gene Expression at the Molecular Level
1. Bread mold can grow in a minimal medium without supplements (wild type) while certain mutated strains
(mutants) can only grow in a minimal medium that is supplemented with specific intermediates found in the following metabolic pathway for arginine synthesis: minimal ------> ornithine -------> citrulline ------> arginine, where enzyme 1 converts the precursor to ornithine, enzyme 2 converts ornithine to citrulline, and enzyme 3 converts citrulline to arginine.
A strain that can grow in a minimal medium containing arginine, but NOT in a minimal medium containing citrulline or ornithine would have a mutation in the gene that encodes for
A. enzyme 1.
B. enzyme 2.
C. enzyme 3.
D. both enzymes 1 and 3.
E. both enzymes 2 and 3.

2. Bread mold can grow in a minimal medium without supplements (wild type) while certain mutated strains
(mutants) can only grow in a minimal medium that is supplemented with specific intermediates found in the following metabolic pathway for arginine synthesis: minimal ------> ornithine -------> citrulline ------> arginine, where enzyme 1 converts the precursor to ornithine, enzyme 2 converts ornithine to citrulline, and enzyme 3 converts citrulline to arginine.
Which of the following would be TRUE of a strain that can grow in minimal medium containing ornithine, citrulline, or arginine, but not in minimal medium alone?
A. The strain would have a mutation in the gene that encodes enzyme 1.
B. The strain would have a mutation in the gene that encodes enzyme 2.
C. The strain would have a mutation in the gene that encodes enzyme 3.
D. The strain would have a mutation in the gene that encodes for enzymes 1, 2, and 3.
E. The strain would be the wild type with no genetic mutations.

3. The process that produces mRNA from DNA is called
A. transcription.
B. translation.
C. replication.
D. processing.
E. post-translational modification.

4. The processes of transcription and translation are collectively known as
A. RNA processing.
B. gene duplication.
C. protein synthesis.
D. DNA synthesis.
E. gene expression.

5. ________ is directly produced from the transcription of a eukaryotic gene.
A. rRNA
B. pre-mRNA
C. mRNA
D. DNA
E. Protein

6. ________ is to transcription as ________ are to translation?
A. RNA splicesome; ribosomes
B. RNA polymerase; ribosomes
C. RNA polymerase; RNA splicesomes
D. DNA polymerase; RNA polymerase
E. DNA polymerase; ribosomes

7. A(n) ______ is an organized unit of DNA sequences that enables a segment of DNA to be transcribed into
RNA and ultimately results in the formation of a functional product.
A. chromosome
B. trait
C. allele
D. gene
E. expression

8. Which of the following are products of nonstructural genes, and are therefore never translated?
A. transfer RNA
B. ribosomal RNA
C. messenger RNA
D. transfer RNA and ribosomal RNA
E. ribosomal RNA and messenger RNA

9. Transcription begins near a site in the DNA called the________, while the terminator specifies the end of transcription. A. promoter
B. enhancer
C. response element
D. transcription unit
E. regulatory sequence

10. Which of the following regions of a structural gene contains the information that specifies an amino acid sequence? A. promoter region
B. transcribed region
C. terminator
D. regulatory sequence
E. enhancer region

11. Which of the following statements about RNA polymerase in bacteria is INCORRECT?
A. It binds the promoter region of a gene.
B. It is bound to a sigma factor during initiation of transcription.
C. It synthesizes RNA.
D. It catalyzes the addition of nucleotides to the 5′ end of a growing RNA strand.
E. It dissociates from the DNA at the terminator.

12. If a DNA template strand has a sequence of 3′ TACAATGTAGCC 5′, then the RNA produced from it will be which sequence?
A. 3′TACAATGTAGCC5′
B. 5′ATGTTACATCGG3′
C. 5′AUGUUACAUCGG5′
D. 3′AUGUUACAUCGG5′
E. 3′ATGTTACATCGG5′

13. Which of the following basic features of transcription is NOT shared by both prokaryotes and eukaryotes?
A. Both prokaryotic and eukaryotic genes have a promotor site.
B. RNA polymerase transcribes genes in both prokaryotes and eukaryotes.
C. Gene transcription involves initiation, elongation, and termination in both prokaryotes and eukaryotes.
D. The complexity of protein components involved in transcription is similar for both prokaryotes and eukaryotes. E. The initiation of transcription in both prokaryotes and eukaryotes involves the interactions of more than one protein. 14. Which of the following proteins is involved in synthesizing messenger RNA in eukaryotes?
A. RNA polymerase I
B. RNA polymerase II
C. RNA polymerase III
D. sigma factor
E. both RNA polymerase I and III

15. Which protein influences the ability of RNA polymerase to transcribe genes?
A. DNA polymerases
B. DNA helicases
C. transcription factors
D. snRNPs
E. tRNA

16. Intervening sequences that are transcribed, but not translated into protein are called
A. exons.
B. introns.
C. splicesomes.
D. transposons.
E. transcription factors.

17. Which of the following would occur if a cell's splicesomes were mutated so they no longer functioned normally? A. Introns would remain in the mature mRNA.
B. Exons would be missing in the mature mRNA.
C. Transcription would cease.
D. A functional protein would still be produced.
E. RNA processing would remain intact.

18. Which of the following statements about RNA processing in eukaryotes is INCORRECT?
A. Introns are excised out of pre-mRNA to produce the mature mRNA.
B. A complex composed entirely of proteins is used to remove introns from the pre-mRNA.
C. A poly A tail is added on to the 3′ end of the mRNA.
D. A 7-methylguanosine cap is added on to the 5′ end of the mRNA.
E. Processing occurs in the nucleus.

19. ________ enables a single gene to encode two or more polypeptides that are different in their amino acid sequence. A. Reverse transcription
B. Self-splicing
C. Capping
D. Alternative splicing
E. Regulatory splicing

20. Which of the following molecule(s) exhibits self-splicing?
A. rRNA
B. tRNA
C. mRNA
D. rRNA and tRNA
E. rRNA and mRNA

21. Which of the following statements about the 5′ cap and mRNA processing is TRUE?
A. The addition of a 5′ cap to mRNA occurs while the pre-mRNA is being made.
B. The 5′ cap helps stabilize the mature mRNA.
C. The 5′ cap prevents the degradation of mature mRNA.
D. The 5′ cap is added to the pre-mRNA by splicesomes.
E. The 5′ cap is a group of adenosine molecules.

22. What is the function of the poly A tail?
A. The poly A tail is required for the proper exit of mRNA from the nucleus.
B. The poly A tail allows mRNA to bind to the ribosome.
C. The poly A tail increases mRNA stability in eukaryotes.
D. The poly A tail increases mRNA stability in prokaryotes.
E. The poly A tail serves as a termination sequence for RNA polymerase III.

23. How many nucleotides are contained in a single codon?
A. 1
B. 3
C. 4
D. 6
E. 9

24. Because more than one codon can specify the same amino acid, the genetic code is said to be
A. repetitive.
B. redundant.
C. reverse.
D. degenerate.
E. degrading.

25. Which of the following statements about the mRNA start codon is INCORRECT?
A. The start codon is only a few nucleotides from the ribosomal binding site.
B. The start codon is usually GGA.
C. The start codon is usually AUG.
D. The start codon specifies the amino acid, methionine.
E. The start codon defines the reading frame.

26. Which of the following is NOT a component of the translation machinery?
A. mRNA
B. tRNA
C. translation factors
D. ribosomes
E. protein polymerase

27. Which of the following serves as the "translator" or intermediary between an mRNA codon and an amino acid? A. rRNA
B. snRNA
C. tRNA
D. siRNA
E. snRNPs

28. On which of the following processes would a defective ribosome have the most detrimental effect?
A. translation
B. replication
C. transcription
D. replication and transcription
E. replication and translation

29. An mRNA sequence is 5′AUG-GGC-ACU-CAU-ACU-UAA3′, where AUG is the start codon and UAA is the stop codon. How many distinct aminoacyl-tRNA synthetases are required to translate the mRNA sequence?
A. 2
B. 3
C. 4
D. 5
E. 6

30. Which factors are needed to recognize the stop codon and disassemble the translation machinery?
A. elongation factors
B. release factors
C. transcription factors
D. inititaion factors
E. mRNA factors

31. What enzyme catalyzes the attachment of amino acids to tRNA molecules?
A. helicase
B. topoisomerase
C. aminoacyl-tRNA synthetase
D. ribosome
E. translation factor

32. If an mRNA sequence is 5′AUG-GGC-ACU-CAU3′, what would the anticodon sequence be?
A. 3′AUG-GGC-ACU-CAU5′
B. 3′UAC-CCG-UGA-GUA5′
C. 5′AUG-GGC-ACU-CAU3′
D. 5′UAC-CCG-UGA-GUA3′
E. 3′TAC-CCG-TGA-GTA3′

33. Which of the following statements about tRNA is FALSE?
A. tRNAs of both eukaryotes and prokaryotes share common features.
B. The two-dimensional structure of tRNAs exhibits a cloverleaf pattern.
C. tRNAs are produced in the nucleus.
D. tRNAs can be spliced by splicesomes.
E. tRNAs possess an anticodon complementary to the codon.

34. The most common eukaryotic ribosome carries out its function in the
A. Golgi apparatus.
B. nucleus.
C. cytosol.
D. mitochondria.
E. chloroplast.

35. Which of the following is released when an aminoacyl-tRNA synthetase charges a tRNA?
A. mRNA
B. ATP
C. AMP
D. pyrophosphate
E. AMP and pryophosphate

36. How many distinct aminoacyl-tRNA synthetases does each cell make?
A. ~1
B. ~20
C. ~60
D. ~120
E. ~180

37. What molecule provides the energy for translation?
A. ADP
B. ATP
C. GMP
D. GDP
E. GTP

38. A ________ bond holds the amino acids of a growing polypeptide chain together during the elongation stage of translation.
A. hydrogen
B. peptide
C. glycosidic
D. noncovalent
E. lactose

39. The term N-terminus refers to the presence of a(n) at the 5′ end of a polypeptide.
A. oxygen atom
B. carboxyl group
C. amino group
D. carbonyl group
E. sulfate group

40. Which sequence of events is most CORRECT for the initiation and elongation steps of translation?
(1) initiator tRNA binds start codon on mRNA
(2) small ribosomal subunit binds to mRNA
(3) large ribosomal subunit binds
(4) tRNA entry and peptidyl transfer reaction
(5) tranlocation of ribosome and release of tRNA
A. 1, 2, 3, 4, 5
B. 1, 2, 3, 5, 4
C. 1, 3, 2, 4, 5
D. 2, 3, 1, 5, 4
E. 2, 1, 3, 4, 5

41. The following codons and the amino acids they encode is as follows:
AUG = Start or Met; UUU, UUC = Phe; UUA, UUG = Leu; UCU, UCC = Ser; CCU, CCC = Pro; ACU, ACC
= Thr; UGA = Stop.
The 5′ACU-UUC-ACU-AUG-UUU-UUA-UCC-UCC-ACU-CCU-UGA3′ mRNA transcript results in which of the following polypeptide sequences?
A. Thr-Phe-Thr
B. Phe-Leu-Ser-Ser-Thr-Pro
C. Met-Phe-Leu-Ser-Ser-Thr-Pro
D. Thr-Phe-Thr-Phe-Leu-Ser-Ser-Thr-Pro
E. Met-Phe-Leu-Ser-Ser