Download Choose the best answer for the following questions

Choose the best answer for the following questions. 2.5 points each question.
1. All of the following factors are required to initiate translation of mRNA in
prokaryotes EXCEPT for
(A) fmet-tRNA
(B) 30S ribosomal subunits
(C) GTP
(D) mRNA
(E) sigma factor
2. All of the following statements about amino acid activation are correct EXCEPT
that
(A) aminoacyl-tRNA synthetases transfer the amino acids to the A on the 3’ end
of tRNA via an aminoacyl-AMP intermediate.
(B) the aminoacyl-tRNA synthetase is specific for a given amino acid.
(C) there may be more than one kind of tRNA for a given amino acid.
(D) The activation step requires the hydrolysis of the terminal phosphate group
of GTP
(E) once an amino acid is attached to a given tRNA the specificity for
recognition of the appropriate codon on mRNA is due entirely to the
tRNA,and not at all to the amino acid
3. Which of the following statements about chain termination in peptide synthesis is
true?
(A) The formation of peptide bonds by the ribosomal mRNA complex continues
until a stop codon on mRNA is reached
(B) The formation of peptide bonds by the ribosomal mRNA complex continues
until a tRNA with an anticodon for UAA, UAG, UGA interacts with the A
site on the ribosome
(C) In prokaryotes, peptide bond formation ceases when an fmet-tRNA interacts
with the A site on the ribosome
(D) Peptide bond formation ceases when the ribosome reaches the 5’ end of the
mRNA
(E) Peptide bond formation continues until the ribosome dissociates into large
and small subunits
4. Which of the following statements about antibiotic inhibitors of protein
synthesis is correct?
(A) Chloramphenicol inhibits the peptidyl transferase activity of the large
ribosomal subunit in eukaryotes
(B) Cycloheximide inhibits the peptidyl transferase activity of the large
ribosomal subunit in eukaryotes
(C) Puromycin blocks protein synthesis in prokaryotes only
(D) Streptomycin inhibits protein synthesis by binding to 50S ribosomal
subunits
(E) Erythromycin inhibits translocation in eukaryotes only
5. The “wobble” hypothesis refers to the less stringent base-pairing specificity of
the
(A) 5’-end base of the codon
(B) 3’-end base of the anticodon
(C) middle base of the anticodon
(D) 5’-end base of the anticodon
(E) middle base of the codon
6. Protein folding is often described as a highly cooperative process. This means that
(A). The folding of a given protein requires cooperation of a number of other proteins
(B). The folding of a protein is largely an all-or-none process
(C). A protein only folds correctly when present in its normal cellular environment.
7. During attachment of an amino acid to its tRNA, how is ATP required?
(A). The free energy of hydrolysis of ATP is used to provide the energy
necessary to link the free amino acid to the tRNA.
(B). The ATP forms an adenylate-tRNA complex that is activated in such a way
that the adenylate can be displaced by the amino acid.
(C). The ATP forms an amino acyl adenylate that transfers the amino acid to the
tRNA.
8. If an amino acid becomes attached to an incorrect tRNA,
(A). the amino acid will be incorporated into protein at the normal sites in the
protein regardless of the tRNA to which it is attached.
(B). the amino acid will be incorporated into protein at sites dictated by the
tRNA even though it is incorrect.
(C). the amino acid will not be used as the ribosome only recognizes amino-acyl
tRNAs which have correct amino acids attached.
9. What distinguishes whether an AUG codon serves as an initiation codon or a
codon for an internal methionine?
(A). Nothing.
(B). A base sequence preceding an AUG which base pairs with 16S rRNA
indicates the AUG will be an initiation codon.
(C). An AUG codon preceded by a three base sequence which specifies another
amino acid must be an internal methionine.
10. Initiation of protein synthesis involves GTP hydrolysis associated with what step?
(A). Dissociation of the 70S ribosome into 30S and 50 S subunits such mRNA
and formyl-methionine tRNAf can bind.
(B). Binding of the mRNA and formyl-methionine tRNAf to the 30 S subunit of
the ribosome.
(C). Binding of the 50S subunit to the 30S subunit with bound mRNA and
formyl-methionine tRNAf.