Unit 5: RNA and Protein Synthesis and Processing - Practice Quiz

1 Which enzyme is responsible for synthesizing RNA during transcription in prokaryotes?

2 Which subunit of prokaryotic RNA polymerase is required for recognizing the promoter sequence?

3 Which RNA polymerase transcribes protein-coding genes (mRNA) in eukaryotes?

4 The TATA box in eukaryotic genes is a part of which region?

5 Which antibiotic inhibits bacterial transcription by binding to RNA polymerase?

6 -Amanitin, a toxin from mushrooms, primarily inhibits which enzyme?

7 The 5' cap added to eukaryotic mRNA is composed of which modified nucleotide?

8 What is one major function of the 5' cap on eukaryotic mRNA?

9 During RNA splicing, which segments are removed from the pre-mRNA?

10 Which cellular machine carries out the splicing of pre-mRNA in eukaryotes?

11 Polyadenylation adds a tail of which nucleotide to the 3' end of eukaryotic mRNA?

12 The poly-A tail added to mRNA primarily helps in which of the following?

13 Which amino acid is carried by the initiator tRNA in prokaryotic translation?

14 Which ribosomal subunit sizes are found in prokaryotes?

15 What is the size of the complete eukaryotic ribosome?

16 Which site on the ribosome holds the growing polypeptide chain during translation?

17 Which antibiotic inhibits translation by binding to the 30S ribosomal subunit and causing misreading of mRNA?

18 Chloramphenicol inhibits protein synthesis by blocking which enzymatic activity?

19 Which of the following is a common chemical post-translational modification of proteins?

20 Proteolytic cleavage of a protein involves which of the following?

21 In E. coli, a mutation in the (sigma) subunit of RNA polymerase would most directly affect which step of transcription?

22 A bacterial gene ends in a GC-rich palindrome followed by a run of A residues on the template. What type of termination does this predict?

23 Which RNA polymerase would be inhibited if a drug specifically blocked transcription of the genes encoding mRNAs in a human cell?

24 The general transcription factor TFIIH possesses helicase and kinase activities. Its kinase activity contributes to transcription by:

25 Rifampicin is effective against bacterial infections because it:

26 -Amanitin from the death cap mushroom is lethal in humans primarily because it:

27 The 5' cap of eukaryotic mRNA is joined to the first nucleotide through an unusual linkage. Which linkage is it?

28 If the enzyme guanylyltransferase were non-functional in a eukaryotic cell, the most likely consequence for mRNA would be:

29 During spliceosome-mediated splicing, the branch point adenosine plays what role in the first transesterification reaction?

30 A single pre-mRNA gives rise to several different protein isoforms in different tissues. This is best explained by:

31 Which snRNP is responsible for recognizing the 5' splice site of an intron at the start of spliceosome assembly?

32 The cleavage and polyadenylation of a eukaryotic pre-mRNA is triggered by recognition of which conserved signal sequence?

33 The poly-A tail added to eukaryotic mRNA is synthesized:

34 In prokaryotes, the ribosome is positioned correctly on the mRNA start codon by base-pairing between the 16S rRNA and which mRNA element?

35 The first amino acid incorporated during prokaryotic translation is carried by a special initiator tRNA. This amino acid is:

36 In eukaryotic translation initiation, the small ribosomal subunit typically locates the start codon by:

37 During elongation, the movement of the ribosome by one codon along the mRNA (translocation) in eukaryotes is powered by:

38 Diphtheria toxin kills human cells by ADP-ribosylating and inactivating eEF2. The direct result is:

39 Why can chloramphenicol be used as an antibacterial agent with relatively low toxicity to the cytoplasmic ribosomes of human cells?

40 The addition of a phosphate group to serine, threonine, or tyrosine residues of a protein is best described as:

41 In E. coli, a mutation in the rpoB gene alters the subunit of RNA polymerase such that the enzyme fails to respond to the intrinsic terminator hairpin but still terminates normally at Rho-dependent sites. Which mechanistic interpretation best explains this phenotype?

42 During RNA Pol II transcription, the C-terminal domain (CTD) undergoes a defined phosphorylation cycle. If a kinase inhibitor selectively blocks CDK7 (part of TFIIH) but not CDK9 (P-TEFb), what is the most direct consequence?

43 Rifampicin inhibits bacterial transcription but has essentially no effect once a transcript exceeds a few nucleotides. Which observation best accounts for this length-dependence?

44 The 5' cap is added co-transcriptionally after only ~25–30 nucleotides are synthesized. Which enzymatic sequence and requirement correctly describes cap formation?

45 In the two transesterification reactions of pre-mRNA splicing, what is the nucleophile and product of the FIRST step?

46 Cleavage and polyadenylation of a pre-mRNA depends on cis-elements flanking the cleavage site. Which combination of signals and their bound factors correctly positions the cut?

47 A bacterial mRNA has a Shine-Dalgarno sequence spaced abnormally far (15 nt) from the start codon. What is the most likely translational consequence?

48 During prokaryotic elongation, GTP hydrolysis occurs at two distinct steps. Which pairing of factor and GTP-dependent role is correct?

49 In cap-dependent eukaryotic initiation, eIF4E binds the m7G cap while the 43S complex scans for the start codon. If eIF4E is sequestered by hypophosphorylated 4E-BP, what happens?

50 Diphtheria toxin catalyzes ADP-ribosylation of a modified histidine residue (diphthamide) in eukaryotic elongation factor 2 (eEF2). What is the direct functional outcome?

51 Puromycin causes premature chain release in both prokaryotes and eukaryotes. Which structural feature explains its mechanism?

52 A secreted protein contains the sequon N-X-S where X is proline. Despite the presence of asparagine, N-linked glycosylation does not occur at this site. Why?

53 -carboxylation of glutamate residues in clotting factors requires vitamin K as a cofactor. Warfarin inhibits this modification. What is the biochemical basis?

54 Proinsulin is converted to mature insulin by proteolytic processing. Which statement correctly describes the events?

55 During protein splicing, an internal intein is excised and the flanking exteins are ligated. Which feature is essential at the intein's C-terminal splice junction for excision to proceed?

56 -amanitin from death cap mushrooms shows differential sensitivity among the three eukaryotic RNA polymerases. Which ranking of sensitivity is correct?

57 The factor recognizes -10 and -35 promoter elements. A promoter with an extended -10 motif (TGn upstream of the -10 box) can function even with a weak or absent -35 element. What is the mechanistic reason?

58 A point mutation converts the invariant GU at a 5' splice site to GC. Alternative splicing analysis shows partial exon skipping. Which explanation best fits?

59 Histone mRNAs in metazoans are unusual among protein-coding transcripts because they typically lack a poly(A) tail. How is their 3' end formed instead?

60 Phosphorylation of eIF2 by kinases such as PKR or PERK causes a global reduction in translation initiation. What is the molecular basis of this repression?