MBLG1001 Past Paper
Questions 33-46
Central Dogma
33. Transcription
•
Which of the following statements about transcription
in procaryotes is TRUE?
A.
After cell division, the entire genome is copied into mRNA as a
back-up.
crazy!
B.
During transcription, both strands of DNA are simultaneously
copied in opposite directions.
no
C.
During transcription, the 3’ end of mRNA remains attached to
the DNA template.
yes!
D.
Before a gene is transcribed, its entire length must be
unwound into single stranded DNA. no
E.
As RNA polymerase transcribes a gene, the sigma subunit
unwinds DNA ahead of it.
sigma falls off after initiation
34. Termination of Transcription
•
Which of the events results in TERMINATION of
procaryotic transcription?
A.
When RNA polymerase reaches a STOP codon.
translation stop signal
B.
When the rho protein falls off RNA polymerase
rho kicks off RNA pol
C.
When the RNA polymerase reaches the START codon for the
next gene.
another translation theme
D.
When a recently transcribed part of mRNA forms intramolecular base pairs
factor independent termination
E.
When the transcription bubble reaches a section of DNA that is
blocked by a group of stationary holoenzymes.
plausible but genes not that close
35. Polycistronic mRNAs
•
Which statement regarding polycistronic mRNAs is
TRUE?
A.
A single polycistronic mRNAs can be translated to give several
proteins.
the definition of polycistronic!
B.
A polycistronic mRNA contains just one start and one stop
codon.
must have one for each protein
C.
Polycistronic mRNAs are the only transcripts that can be
produced in multiple copies after initiation of a gene.
all mRNAs have this potential
D.
Polycistronic mRNAs are the only transcripts that can be
simultaneously translated as they are being transcribed
all mRNAs have this potential
E.
Polycistronic mRNAs are formed by post-transcriptional
splicing of small transcripts.
would be interesting, but no! More interesting if bits of
protein could!
36. CAP
•
What does NOT describe the function of the
procaryotic catabolite activator protein (CAP)?
A. CAP binds to the DNA downstream of the initiation
site
binds upstream at promoter
B. CAP displaces the repressor from DNA
repressor has its own site
C. CAP interacts with the alpha subunits of RNA
polymerase
it does
D. CAP requires cyclic AMP to properly bind to DNA
it does
E. After binding to DNA, CAP simulates the
transcription of genes it does
37. Repressor
•
Which statement BEST describes the function of the
repressor used to regulate expression of the gene that
codes for lactose metabolizing enzymes?
A.
This repressor also inhibits expression of the genes that code
for glucose metabolism. glucose not inducible – important!
B.
Binding of lactose to this repressor lessens it’s affinity for DNA.
removes the inhibition
C.
This repressor is only produced when lactose is around.
repressor produced constitutively
D.
This repressor stimulates the termination of transcription.
just inhibits initiation
E.
This repressor displaces CAP from the DNA.
geographically separate binding sites
38. Translation Direction
•
Which of the following statements about directionality
in procaryotic translation is FALSE?
A.
The mRNA is translated in the 5’ to 3’ direction.
it is!
B.
Codon:anti-codon base pairing is complementary and antiparallel
all base pairing is
C.
The protein is made in the C- to N- direction.
D.
The ribosome moves down the mRNA in the 5’ to 3’ direction
other way – N-fmet group at start
relatively speaking
E.
The tip of a polypeptide chain emerging from a ribosome is a
formyl group.
similar to C
39. Ribosomes
•
Which of the following statements regarding
procaryotic ribosomes is CORRECT?
A.
The 30S and 50S subunits are held together by proteins called
initiation factors
actually kept apart by the initiation factors
B.
The 50 S subunit contains 16 S rRNA this is in the 30 S subunit
C.
The 30 S subunit contains rRNA that catalyses the formation
of the peptide bond this is in the 30 S subunit
D.
A mixture of ribosomal RNAs and proteins can self assemble
to produce functional ribosomes
they sure can!
E.
The 30 S subunit contains the P- and A-sites for tRNA
these caverns are in the big one
40. Translation Elongation
•
Which statement regarding the elongation phase of
procaryotic protein synthesis is FALSE?
A.
In the aa-tRNA coming into the ribosome, the carboxylic acid
group of the amino acid is in a bond with the tRNA.
correct. remember N-formy-met on end
B.
During peptide bond formation, the peptide on the tRNA at the
P-site moves onto the tRNA at the A-site.
correct. strange to move the big bit!
C.
Empty tRNAs are ejected before the ribosome moves down
the mRNA
not until the ribosome moves on
D.
EF-G catalyses the relative movement of the ribosome and the
mRNA
translocase
E.
New aa-tRNAs come into the A-site
yes
41. Translation
•
Which statement about procaryotic translation is
TRUE?
A.
Only polycistronic mRNAs can be translated by more than one
ribosome at a time they all can
B.
An mRNA can only be translated once it has been fully
transcribed
can be simultaneous
C.
The rate of transcription of mRNA is much faster than the rate
of translation
both 40 nucleotides/s
D.
The rate of translation of mRNA is much faster than the rate of
transcription. both 40 nucleotides/s
E.
The presence of polysomes makes an mRNA less prone to
nuclease digestion
less easy for nucleases to attack
42. Degeneracy & Wobble
•
Considering that there is degeneracy and wobble in
the code, which statement about the relationship
between mRNA and protein sequence is TRUE?
A.
Given an amino acid sequence of a protein, it would be
impossible to predict the correct nucleotide sequence of its
mRNA
can’t tell which codons used
B.
Given an amino acid sequence of a protein, it would be
possible to predict the correct nucleotide sequence of its DNA.
as for A
C.
Given an mRNA sequence, it would be impossible to
determine the amino acid sequence of the protein
just need the table of Genetic Codes
D.
Sequence predictions are only possible in some species
a silly statement
E.
Given the DNA sequence, it would be impossible to determine
the amino acid sequence of the protein.
if know DNA, know RNA and thus protein
43. Pro vs Eu
•
Which statement regarding the differences between
procaryotic and eucaryotic molecular biology is
FALSE?
A.
In eucaryotes, DNA is located in organelles
nucleus
B.
In eucaryotes, DNA is wrapped around a core of protein
histones, nucleosomes, chromatin
C.
In procaryotes, most of the DNA is in introns
no introns/exons in procaryotes
D.
In eucaryotes, mRNA must be transported into the cytoplasm
before translation more precisely the endoplasmic reticulum
E.
mRNA molecules tend to be longer-lived in eucaryotes
they are
44. Eucaryotic Transcription
•
Which statement regarding eucaryotic transcription is
FALSE?
it is made by RNA pol II
A.
mRNA is transcribed by RNA polymerase II
B.
Sections of DNA that are being transcribed are more prone to
nuclease digestion
naked
C.
Eucaryotic promoters bind multiple transcription factors
very complicated
D.
Eucaryotic enhancer sequences can be located within the
transcribed portion of the gene
almost anywhere in fact
E.
The eucaryotic promoter sequence is the same as the
procaryotic consensus sequenece.
similar but not identical
45. mRNA Processing
•
During post-transcriptional processing, what does NOT
happen to a primary mRNA transcript?
A.
A guanine nucleotide is attached to the 5’ end
B.
Several hundred adenine nucleotides are attached to the 3’
end
tailing
C.
Intronic sequences are cut out and assembled into a mature
transcript
splicing… but introns are destroyed!
D.
The transcript is acted on by spliceosomes
E.
The transcript is cleaved by small nuclear ribonuceloproteins
capping
splicing apparatus
components of spliceosomes
46. Eucaryotic Translation
•
Which statement about the initiation of eucaryotic
translation is TRUE?
A.
The mRNA binds to the ribosome through the Shine Dalgarno
sequence
procaryotic. scanning in eucaryotes
B.
The first tRNA to come in contains N-formyl-methionine
just plain old met
C.
The first AUG codon in the transcript is normally the first to be
translated
scanning
D.
The 5’ cap of mRNA is positioned into the P-site
first AUG in P-site
E.
The initiating complex is between the mRNA and the 60 S
subunit
the 40S subunit