1. Ribosomes consist of two dissociable subunits called the large and small subunits, which
only come together when bound to mRNA. Transfer RNAs (tRNAs) bring amino acids to
the ribosome to start prokaryotic translation following which of the following, initiator
tRNAs?
a. IF-2 bound to GTP.
b. tRNAmet.
c. Shine-Dalgarno sequence.
d. Any tRNA with AUG as a start codon.
e. tRNAfMet.
2. What is the initiator tRNA in eukaryotes?
a. tRNAfMet.
b. Kozac Sequence.
c. tRNAMet.
d. IF-2 bound to GTP
e. Shine-Dalgarno sequence.
3. What is the function of the formyl group present in tRNAfMet?
a. The formyl group protects the mRNA from nucleolytic degradation.
b. The formyl group blocks the amino group of methionine so it cannot form
peptide bonds with other amino acids. Only the carboxyl group is available for
bonding, making it an initiator tRNA.
c. The formyl group blocks the carboxyl group of methionine so it cannot form
peptide bonds. Since translation also occurs in the 3’ 5’ direction, this allows
for a greater diversity of polypeptides.
d. In Eukaryotes, the formyl group blocks the amino group, preventing formation of
peptide bonds. Translation is carried out by the ribosome in the NC direction,
so this makes tRNAfMet the initiator tRNA.
e. None of the following choices can be applied to tRNAs, because the formyl group
does not have a carbon atom to attach to the amino acid.
4. The initiator tRNA, generated via the AUG start codon, resides in which of the following
areas of the ribosome to start translation?
a. A site
b. E site
c. Depends on the polypeptide being synthesized.
d. P site
e. Both A and C
5. The amino acid attaches to which of the following sequences on the tRNA?
a. AUG
b. UGA
c. The position with the most 3rd base wobble potential
d. CCA
e. IGC
6. What feature of the sequence you selected above allows amino acids to attach to the
tRNA?
a. 3’-OH group
b. 5’-OH group
c. Guanosine residue
d. Hydroxyl group
e. Both A and D
7. Eukaryotic tRNAs can recognize codons in mRNA because each tRNA possesses:
a. Anticodon sequences that base pair to the mRNA in the nucleus.
b. Codon sequences that base pair to the mRNA in the cytosol.
c. Anticodon sequences that base pair to the mRNA in the cytosol.
d. 3rd base wobble potential.
e. Both A and C
8. Which of the following third position bases are the “Wobbliest”, since it can base pair
with U,C and A?
a. A, because it can base pair with U.
b. I
c. A tie between G and I
d. G, because it can base pair with C and U
e. Not listed.
9. Why does wobble not cause insertion of incorrect amino acids?
a. Wobble means that a single tRNA can recognize more than one codon, but the
different codons recognized by a given tRNA always code for the same amino
acid.
b. Wobble ensures that amino acids are always translated in the NC direction.
c. Wobble means that multiple tRNAs recognize only one codon, so there is no
room for error in translation.
d. Both A and C, depending on if it is prokaryotic or Eukaryotic translation we are
considering.
e. All of the above, prokaryotic and eukaryotic translation utilize the same
mechanisms and proteins.
10. Once the correct amino acid has been joined to its tRNA, which of the following
recognizes the appropriate codon in mRNA?
a. The large subunit
b. The CCA sequence
c. The amino acid
d. The small subunit
e. tRNA
11. Which of the following stop codons are recognized by RF-1?
a. UAA and UAG
b. UGA
c. UAG
d. UAA and UAG
e. UAA and UGA
12. Condons in mRNA recognize_______________ rather than__________________.
Hence, the specifity of the Aminoacyl-tRNA synthetase reaction is critical for the
accurate expression of genes.
a. tRNAMet/ Cytosine.
b. Bound amino acids/ tRNA molecules.
c. tRNA molecules/ bound amino acids.
d. Kozac sequences/ Shine-Dalgarno sequences.
e. 5’ cap/ Polyadenylated tail.
13. Translation of polypeptides begins with the synthesis of polypeptides at its ________,
and sequentially adds amino acids to the growing chain until it meets
the___________________.
a. C terminus/ Amino terminus.
b. Kozac sequence/ Stop codon AUG.
c. 5’ Cap/ Polyadenylated tail.
d. N terminus/ Carboxyl terminus.
e. Shine Dalgarno sequence/ Stop codon AAUAAA.
14. GTP binds to which of the following protein factors to begin translation?
a. IF-1
b. EF-Tu
c. EF-G
d. Both IF-2 and IF-3
e. IF-2
15. Which of the following elements hydrolyze GTP to drive translation in prokaryotes?
a. 40S subunit.
b. GTP is not hydrolyzed, ATP is.
c. 50S subunit.
d. 30S subunit.
e. 70S initiation complex.
RXN 1:
RXN 2: ATPAMP + PPi
RXN 3:
a. AA + ATP AA-AMP + Pyrophosphate (2Pi)
b. AA-AMP AA-tRNA + AMP
RXN 4: PPi + H2O 2Pi
16. Aminoacyl-Adenylate is said to be a “High-Energy compound”. From what you know
about the catalytic mechanism of Aminoacyl-tRNA Synthetase, which bond in RXN 1
makes Aminoacyl-Adenylate this “High-Energy compound”?
a. Bond A, an anhydride bond.
b. Bond C, an ester bond.
c. Bond B, a hydrogen bond.
d. Bond A, an ester bond.
e. All of the above, because of resonance stabilization. This makes every bond in
RXN 1 “High-Energy”.
17. What is the energy provided from the bond you selected above used for in eukaryotic
cells?
a. Peptide bond formation in the nucleus during transcription.
b. Splicing glyceraldehyde- 3- phosphate into fructose-1, 6- bisphosphate in
gluconeogenesis.
c. Peptide bond formation in the nucleus during translation.
d. Peptide bond formation in the cytosol during transcription.
e. Peptide bond formation in the cytosol during translation.
18. Aminoacyl tRNA Synthetase catalyzes the joining of amino acids to its corresponding
tRNAs via ester bonds, accompanied by the hydrolysis of ATP to AMP and
pyrophosphate. Which reaction above depicts the catalytic action of Aminoacyl-tRNA
synthetase?
a. RXN 4
b. RXN 1
c. RXN 3, “step a” only.
d. RXN 3, “step b” only.
e. Both RXNs 1 and 3.
19. RXN 3 was written very deceptively, only in the sense that it does not provide the
observer with an understanding of the importance of the reactants and products. Which
of the following options show why RXN is very misleading?
a. RXN 3 depicts ATP as the ultimate provider of energy, whereas the energy truly
comes from PPi. (Not shown).
b. 2Pi is the shorthand for inorganic phosphate, and not pyrophosphate.
c. Pyrophosphate has been labeled as “2Pi”, in fact pyrophosphate should be
shorthanded as PPi.
d. The writer of the reaction has failed to understand basic chemical nomenclature.
e. All of the above choices are correct.
20. RXN 1 is a better depiction of the catalytic mechanism Aminoacyl-tRNA synthetase,
which is said to produce a “High-Energy compound” Aminoacyl-Adenylate. The enzyme
is also said to function in “amino acid activation”. Which bond shown in RXN 1 proves
both of these statements correct?
a. Bond A, an anhydride bond, which make ribosomes enthalpy traps.
b. Bond C, makes the molecule a strong acid that can cleave peptide bonds.
c. Bond A, upon hydrolysis will provide enough energy for subsequent peptide
bond formation.
d. Bond D, a hydrogen bond, acts as a base catalyst.
e. None of the above bonds show that both of the above statements are correct.
21. Which reaction above provides the energy that drives the entire reaction that describes
the catalytic mechanism of Aminoacyl-tRNA Synthetase?
a. RXN 1
b. RXN 4
c. RXN 3
d. The reaction is not shown
e. All of the above, the energy comes from the electrons carried by NADH as this
coenzyme scrapes by the substrates and picks up the energy. This energy is then
used to perform other functions in the cell.
22. Which of the following elements are required for eukaryotic translation initiation?
a. tRNAMet + eIF-2 with GTP already attached before tRNA binds to the small
subunit and other initiation factors. This complex binds to the 5’ end of mRNA by
recognizing the 5’ cap.
b. tRNAFMet + eIF-2 with GTP already attached before tRNA binds to the small
subunit and other initiation factors. This complex binds to the 5’ end of mRNA by
recognizing the 5’ cap.
c. tRNAMet + eIF-3 with GTP already attached before tRNA binds to the small
subunit and other initiation factors. This complex binds to the 5’end of mRNA by
recognizing the 5’ cap.
d. tRNAFMet + eIF-3 with GTP already attached before tRNA binds to small subunit
and other initiation factors. This complex binds to the 5’ end of mRNA by
recognizing the 5’ cap.
e. None of the following function in eukaryotic initiation translation.
23. Regarding eukaryotic translation, which of the following nucleotides apart of a special
sequence are absolutely critical for initiation?
a. Eukaryotic translation initiation requires a Shine-Dalgarno sequence (AGGAGG)
with AGGA being the key nucleotides.
b. Eukaryotic translation requires a Kozac sequence (ACCAUGG) with UGG being
the key nucleotides.
c. Eukaryotic translation requires a Kozac sequence (ACCAUGG) with AUG being the
key nucleotides.
d. Eukaryotic translation initiation requires a Shine-Dalgarno sequence (AGGAGG)
with GAG being the key nucleotides.
e. Eukaryotic translation initiation requires a Kozac sequence (ACCAUGG) with ACC
being the key nucleotides.
24. Which of the following statements are true?
a. When the large subunit of the ribosome base pairs with the small subunit, the
mRNA binds to the complex. After this the tRNAMet binds and initiation is now
complete.
b. When the large subunit of the ribosome joins the small subunit, the mRNA binds
to the complex. After this the tRNAFMet binds and eukaryotic initiation is now
complete.
c. When the large subunit of the ribosome joins with the small subunit, the mRNA
binds to the complex tRNAfMet binds last and eukaryotic translation initiation is
complete.
d. When the initiator tRNAMet base pairs with the start codon on the mRNA, the
large subunit then joins with the small subunit and eukaryotic translation
initiation is complete.
e. None of the statements are true.
25. Chain elongation in eukaryotes follows which order?
a. Binding of aminoacyl-tRNA to the ribosome, peptide bond formation, mRNA
molecule is advanced 3 codons by process of transduction.
b. The mRNA molecule is advanced 3 codons, the aminoacyl-tRNA binds to the
ribosome, and the peptide bond forms through the process of transduction.
c. Binding of aminoacyl-tRNA to the ribosome, the mRNA molecule is advanced
three codons, and the peptide bond is formed through the process of
transduction.
d. GTP hydrolysis, ATP binding, and then the binding of aminoacyl-tRNA.
e. Chain elongation in eukaryotes follows all of these orders, depending on
whether ATP, GTP and pyrophosphate are present at saturating conditions as
predicted by Michaelis-Menton kinetics.
26. Eukaryotic polypeptide chain elongation begins when:
a. An aminoacyl-tRNA whose anticodon is complimentary to the second codon
binds to the ribosomal A site. The start codon is located in the P site.
b. An amino-acyl-tRNA whose codon is complimentary to the second codon binds
to the ribosomal A site. The start codon is located in the P site.
c. An aminoacyl-tRNA whose anticodon is complimentary to the second codon
binds to the ribosomal P site. The start codon is located in the A site.
d. An amino-acyl-tRNA whose codon is complimentary to the second codon binds
to the ribosomal A site. The start codon is located in the P site.
e. This process describes initiation, not polypeptide chain elongation.
27. Binding of new aminoacyl-tRNA to the codon in the ___________ requires __________
and________. This is driven by the hydrolysis of ____________.
a. A site/ EF-Ts/ EF-Tu/ ATP
b. P site/ EF-Tu/ EF-Ts/ ATP
c. E site/ EF-Ts/EF-Tu/ GTP
d. A site/ EF-Tu/ EF-Ts/ GTP
e. P site/ EF-Tu/ EF-Ts/GTP
28. What is the function of EF-Tu?
a. When bound to ATP, EF-Tu conveys aminoacyl-tRNA to the A site of the
ribosome. The EF-Tu-GTP complex promotes the binding of all aminoacyl-tRNAs
except the initiator tRNAs.
b. When bound to ATP, EF-Tu conveys aminoacyl-tRNA to the P site of the
ribosome. The EF-Tu-GTP complex promotes the binding of all aminoacyl-tRNAs
except the initiator tRNAs.
c. When bound to GTP, EF-Tu conveys aminoacyl-tRNA to the A site of the
ribosome. The EF-Tu-GTP complex promotes the binding of all aminoacyl-tRNAs
except the initiator tRNAs.
d. When bound to GTP, EF-Tu conveys aminoacyl-tRNA to the P site of the
ribosome. The EF-Tu-GTP complex promotes the binding of all aminoacyl-tRNAs.
e. When bound to GTP, EF-Tu conveys aminoacyl-tRNA to the A site of the
ribosome. The EF-Tu-GTP complex promotes the binding of all aminoacyl-tRNAs.
29. What is the nucleotide sequence of the tRNA that carries the first amino acid and binds
to the start site?
a. AUG codon
b. AUG anticodon
c. UAC anticodon
d. UAG codon
e. UAC codon
30. The first three initiation factors bind to which of the following subunits in prokaryotes?
a. 20S
b. 30S
c. 16S
d. 40S
e. 50S
31. The prokaryotic mRNA binding site is comprised of:
a. The pyrimidine (ACCAUGG) Kozac sequence complimentarily base paired with
the 5 and 23S rRNA in the ribosomal small subunit.
b. The 5’ cap, the Kozac sequence of purines (ACCAUGG) and GTP
c. The purine (ACCAUGG) Kozac sequence complimentarily base paired with the
3’pyrimidines of the 16S rRNA in the ribosomal small subunit.
d. The purines (AGGA) Shine-Dalgarno sequence complimentarily base paired with
the 3’ pyrimidines of the 16S rRNA in the ribosomal small subunit.
e. The purines (AGGA) Shine-Dalgarno sequence complimentarily base paired with
the 3’ pyrimidines of the 5S rRNA in the ribosomal small subunit.
32. During prokaryotic initiation, the initiator tRNA with attached N-Formyl methionine is
bound to the P site of the ____________ribosomal subunit by the action of the initiation
factor__________ bound to _____________.
a. 50S/IF-1/GTP
b. 60S/IF-2/UTP
c. 40S/IF-3/ATP
d. 30S/IF-2/GTP
e. 70S/IF-2/GTP
33. What is the role of EF-Ts?
a. Regeneration of EF-Tu-GTP from EF-Tu-GDP for the next round of elongation.
b. To act as a ribozyme.
c. Regeneration of EF-Tu-GDP from EF-Tu-GTP for the next round of elongation.
d. To act as a base catalyst.
e. EF-Ts functions in all of these roles, because that is the definition of a ribozyme.
34. Why is 23S rRNA an example of a ribozyme?
a. In eukaryotic rRNA, 23S rRNA is responsible for peptidyl transferase activity
rather than the ribosomal proteins.
b. In prokaryotic rRNA, 23S rRNA is responsible for peptidyl transferase activity
rather than the ribosomal proteins.
c. In prokaryotic rRNA 5S rRNA is responsible for peptidyl transferase activity rather
than the ribosomal proteins.
d. In human rRNA, 23S rRNA is responsible for peptidyl transferase activity rather
than the ribosomal proteins.
35. The translocation process requires which of the following elements?
a. EF-G + Pyrophosphate
b. EF-G + GTP
c. EF-Tu + GTP
d. EF-Tu +ATP
e. EF-Tu +UTP
36. Polypeptides are synthesized by the ribosome at a rate of:
a. 400 amino acids every 10 seconds
b. 30 amino acids every 10 seconds
c. 40 amino acids every second
d. Ribosomes don’t synthesize polypeptides
e. Both answers A and C.
Answer Key:
1. E
2. C
3. B
4. D
5. D
6. E
7. C
8. B
9. A
10. E
11. D
12. C
13. D
14. E
15. C
16. D
17. E
18. E
19. E
20. C
21. B
22. A
23. C
24. D
25. A
26. A
27. D
28. C
29. C
30. B
31. D
32. D
33. A
34. B
35. B
36. E