BCH 5413 Exam 3 -Questions With
100% Verified Answers.
One tRNA can pair with multiple codons through non-Watson/Crick base pairing (G=U) -
✔✔What is the significance of the wobble hypothesis?
True (AMP derived from ATP is used to catalyze bond formation between the amino acid
and the tRNA) - ✔✔T/F: aminoacylation of tRNAs requires ATP.
True (GTP is required for the binding of aminoacyl-tRNA to the A site of the ribosome) -
✔✔T/F: protein synthesis requires GTP.
False (one aminoacyl-tRNA can pair with multiple codons, but one codon cannot pair with
multiple tRNAs) - ✔✔T/F: wobble allows different aminoacyl-tRNAs to pair with
same codon.
False (the bond formation between the amino acids and tRNAs is catalyzed by aminoacyl-
tRNA SYNTHETASE) - ✔✔T/F: ligase enzyme joins the amino acids to the respective
tRNAs.
False (it requires ATP) - ✔✔T/F: aminoacylation of tRNAs requires GTP.
False (fmet-tRNA is in prokaryotes; met-tRNA is in eukaryotes) - ✔✔T/F: fmet-tRNA is
the initiator tRNA in eukaryotes.
Prokaryotes: a ribosome binding site in front of the operon; eukaryotes: the 5' cap - ✔✔Where
does the ribosome bind to the mRNA in prokaryotes vs. eukaryotes?
True (but multiple proteins can be produced from a singular mRNA in prokaryotes) - ✔✔T/F:
there is generally only 1 protein produced per mRNA in eukaryotes.
,ATP - ✔✔What is required in order for the mRNA to be "unwound" during translation
in eukaryotes?
False (it only regulates translation in eukaryotes) - ✔✔T/F: phosphorylation regulates
translation in both prokaryotes and eukaryotes.
It binds to the A site in the 30S ribosome, preventing fmet-tRNA from binding - ✔✔What
is the function of IF1?
It binds fmet-tRNA and GTP, bringing the complex to the P site for GTP hydrolysis -
✔✔What is the function of IF2?
IF2 - ✔✔Which IF is able to bind GTP (in bacteria)?
It keeps the 30S and 50S subunits separate - ✔✔What is the function of IF3?
The 30S subunit - ✔✔Which ribosomal subunit binds to the ribosomal binding site (rbs)
in prokaryotes?
After (the 50S subunit must also be present for GTP hydrolysis to occur) - ✔✔Does GTP
hydrolysis occur BEFORE or AFTER the 70S subunit is formed?
(1) IF3 dissociates from the 30S subunit -> (2) the 50S subunit binds forming the 70S complex -
> (3) GTP hydrolysis occurs, releasing IF2 and allowing polypeptide formation to begin -
✔✔What are the 3 steps in formation of the 70S complex?
To release IF2 from the complex, allowing formation of the polypeptide chain - ✔✔What
is the function of GTP hydrolysis in the formation of the 70S complex?
Segments of mRNA in front of operons (in prokaryotes) that specific sections of
rRNA complementary base pair to - ✔✔What are ribosomal binding sites (rbs)?
,The amino group does a nucleophilic attack on the adjacent amino acid's carboxyl group -
✔✔During peptide bond formation, which functional group attacks which? Which type
of "attack" occurs?
(1) The aminoacyl-tRNA binds to the A site by matching its anticodon to the correct codon ->
(2) a peptide bond forms between adjacent amino acids -> (3) EGF-G causes translocation of the
tRNA from the A site to the P site - ✔✔What are the 3 main steps of elongation?
It is needed during both step 1 and 3 of elongation - ✔✔When is GTP needed
during elongation?
It is needed to align the aminoacyl-tRNA to the A site (step 1) and to translocate the tRNA from
the A site to the P site (step 3) - ✔✔Why is GTP needed during elongation?
The ribosome reaches a stop codon in the mRNA and release factors + GTP enter the A site -
> GTP hydrolysis occurs -> the ribosome subunits dissociate and the polypeptide is released -
✔✔How does translation stop?
GTP hydrolysis (in the A site) - ✔✔What reaction causes the polypeptide to be released
from the ribosome?
The order that the nucleotides in mRNA is read by the ribosome (frameshifts of 1 nucleotide can
cause a completely different amino acid sequence to be translated) - ✔✔What is indexing?
A primer + reverse transcriptase allows elongation until the P site is reached; wherever the new
strand ends are the nucleotides that make up the codon in the P site - ✔✔How does toe-
printing allow researchers to determine the codon that is in the P site?
All 3 initiation factors - ✔✔Toe-printing experiments show that in order to ratchet to
the correct reading frame, indexing requires:
, 1-3 minutes (very short!) - ✔✔What is the lifetime of bacterial mRNA?
The mRNA (it is the ribosomal binding site that the rRNA binds to) - ✔✔Is the
Shine-Dalgarno sequence located in the rRNA or the mRNA?
Linear mRNA is easily translated (if 1 cistron is in a hairpin structure it will not be translated as
often as cistrons that are linear) - ✔✔How does the secondary structure of mRNA affect
translation from a polycistronic message?
False (eukaryotic mRNA is a polysome, meaning that multiple ribosome can translate it at once)
- ✔✔T/F: only 1 ribosome can translate a eukaryotic mRNA at a time.
The polyA binding proteins (PABPs) on the mRNA's 3' end interact with the initiation
factors bound to the mRNA's 5' cap - ✔✔How do eukaryotic mRNAs become circular in
the cytoplasm?
Ribosome that finish translation are able to be "recycled" for re-initiation of translation,
causing translation to be fast (ribosomes always available) - ✔✔Why is it important for
translation that eukaryotic mRNAs become circular in the cytoplasm?
eIf4e - ✔✔Which initiation factor is required to allow binding between the 40S subunit and
the 5' mRNA cap?
False (mRNA-rRNA binding only occurs in prokaryotes) - ✔✔T/F: binding occurs
between mRNA and rRNA (in initiation) in both prokaryotes and eukaryotes.
False (eukaryotes have many more initiation factors, allowing for more control of translation) -
✔✔T/F: prokaryotes have more initiation factors involved in translation than eukaryotes.
Prokaryotes: EF-Tu binds the tRNA to the A site + EGF-G causes translocation of the tRNA to
the P site; eukaryotes: eEF1-alpha binds the tRNA to the A site + eEF2-G causes translocation of
100% Verified Answers.
One tRNA can pair with multiple codons through non-Watson/Crick base pairing (G=U) -
✔✔What is the significance of the wobble hypothesis?
True (AMP derived from ATP is used to catalyze bond formation between the amino acid
and the tRNA) - ✔✔T/F: aminoacylation of tRNAs requires ATP.
True (GTP is required for the binding of aminoacyl-tRNA to the A site of the ribosome) -
✔✔T/F: protein synthesis requires GTP.
False (one aminoacyl-tRNA can pair with multiple codons, but one codon cannot pair with
multiple tRNAs) - ✔✔T/F: wobble allows different aminoacyl-tRNAs to pair with
same codon.
False (the bond formation between the amino acids and tRNAs is catalyzed by aminoacyl-
tRNA SYNTHETASE) - ✔✔T/F: ligase enzyme joins the amino acids to the respective
tRNAs.
False (it requires ATP) - ✔✔T/F: aminoacylation of tRNAs requires GTP.
False (fmet-tRNA is in prokaryotes; met-tRNA is in eukaryotes) - ✔✔T/F: fmet-tRNA is
the initiator tRNA in eukaryotes.
Prokaryotes: a ribosome binding site in front of the operon; eukaryotes: the 5' cap - ✔✔Where
does the ribosome bind to the mRNA in prokaryotes vs. eukaryotes?
True (but multiple proteins can be produced from a singular mRNA in prokaryotes) - ✔✔T/F:
there is generally only 1 protein produced per mRNA in eukaryotes.
,ATP - ✔✔What is required in order for the mRNA to be "unwound" during translation
in eukaryotes?
False (it only regulates translation in eukaryotes) - ✔✔T/F: phosphorylation regulates
translation in both prokaryotes and eukaryotes.
It binds to the A site in the 30S ribosome, preventing fmet-tRNA from binding - ✔✔What
is the function of IF1?
It binds fmet-tRNA and GTP, bringing the complex to the P site for GTP hydrolysis -
✔✔What is the function of IF2?
IF2 - ✔✔Which IF is able to bind GTP (in bacteria)?
It keeps the 30S and 50S subunits separate - ✔✔What is the function of IF3?
The 30S subunit - ✔✔Which ribosomal subunit binds to the ribosomal binding site (rbs)
in prokaryotes?
After (the 50S subunit must also be present for GTP hydrolysis to occur) - ✔✔Does GTP
hydrolysis occur BEFORE or AFTER the 70S subunit is formed?
(1) IF3 dissociates from the 30S subunit -> (2) the 50S subunit binds forming the 70S complex -
> (3) GTP hydrolysis occurs, releasing IF2 and allowing polypeptide formation to begin -
✔✔What are the 3 steps in formation of the 70S complex?
To release IF2 from the complex, allowing formation of the polypeptide chain - ✔✔What
is the function of GTP hydrolysis in the formation of the 70S complex?
Segments of mRNA in front of operons (in prokaryotes) that specific sections of
rRNA complementary base pair to - ✔✔What are ribosomal binding sites (rbs)?
,The amino group does a nucleophilic attack on the adjacent amino acid's carboxyl group -
✔✔During peptide bond formation, which functional group attacks which? Which type
of "attack" occurs?
(1) The aminoacyl-tRNA binds to the A site by matching its anticodon to the correct codon ->
(2) a peptide bond forms between adjacent amino acids -> (3) EGF-G causes translocation of the
tRNA from the A site to the P site - ✔✔What are the 3 main steps of elongation?
It is needed during both step 1 and 3 of elongation - ✔✔When is GTP needed
during elongation?
It is needed to align the aminoacyl-tRNA to the A site (step 1) and to translocate the tRNA from
the A site to the P site (step 3) - ✔✔Why is GTP needed during elongation?
The ribosome reaches a stop codon in the mRNA and release factors + GTP enter the A site -
> GTP hydrolysis occurs -> the ribosome subunits dissociate and the polypeptide is released -
✔✔How does translation stop?
GTP hydrolysis (in the A site) - ✔✔What reaction causes the polypeptide to be released
from the ribosome?
The order that the nucleotides in mRNA is read by the ribosome (frameshifts of 1 nucleotide can
cause a completely different amino acid sequence to be translated) - ✔✔What is indexing?
A primer + reverse transcriptase allows elongation until the P site is reached; wherever the new
strand ends are the nucleotides that make up the codon in the P site - ✔✔How does toe-
printing allow researchers to determine the codon that is in the P site?
All 3 initiation factors - ✔✔Toe-printing experiments show that in order to ratchet to
the correct reading frame, indexing requires:
, 1-3 minutes (very short!) - ✔✔What is the lifetime of bacterial mRNA?
The mRNA (it is the ribosomal binding site that the rRNA binds to) - ✔✔Is the
Shine-Dalgarno sequence located in the rRNA or the mRNA?
Linear mRNA is easily translated (if 1 cistron is in a hairpin structure it will not be translated as
often as cistrons that are linear) - ✔✔How does the secondary structure of mRNA affect
translation from a polycistronic message?
False (eukaryotic mRNA is a polysome, meaning that multiple ribosome can translate it at once)
- ✔✔T/F: only 1 ribosome can translate a eukaryotic mRNA at a time.
The polyA binding proteins (PABPs) on the mRNA's 3' end interact with the initiation
factors bound to the mRNA's 5' cap - ✔✔How do eukaryotic mRNAs become circular in
the cytoplasm?
Ribosome that finish translation are able to be "recycled" for re-initiation of translation,
causing translation to be fast (ribosomes always available) - ✔✔Why is it important for
translation that eukaryotic mRNAs become circular in the cytoplasm?
eIf4e - ✔✔Which initiation factor is required to allow binding between the 40S subunit and
the 5' mRNA cap?
False (mRNA-rRNA binding only occurs in prokaryotes) - ✔✔T/F: binding occurs
between mRNA and rRNA (in initiation) in both prokaryotes and eukaryotes.
False (eukaryotes have many more initiation factors, allowing for more control of translation) -
✔✔T/F: prokaryotes have more initiation factors involved in translation than eukaryotes.
Prokaryotes: EF-Tu binds the tRNA to the A site + EGF-G causes translocation of the tRNA to
the P site; eukaryotes: eEF1-alpha binds the tRNA to the A site + eEF2-G causes translocation of
