worksheet questions Flashcards
5 + 6 +7 + 8
A bacterial __________ is the non-transcribed region of the DNA to which RNA polymerase binds
in order to initiate transcription.
A) operon
B) operator
C) promoter
D) initiator
promoter
Q2. The site on the DNA to which a repressor protein binds is the __________.
A) operon
B) operator
C) promoter
D) regulator
operator
Q3. Which of these is not a feature of a bacterial promoter?
A) +1
B) -10
C) -18
D) -35
18
Two amino acids that are found in some proteins due to exceptions in the universal genetic code
are _________.
A) pyrrolysine and selenocysteine
B) lysine and selenocysteine
C) pyrrolysine and cysteine
D) lysine and cysteine
pyrrolysine and selenocysteine
Which modification of the terminator region of a gene would specifically prevent rho-independent
termination?
A) Change in the adenine-rich sequence of nucleotides of the terminator region.
B) Change in the adenine-thymine sequence of the Pribnow box.
C) Change in the sequence that encodes the mRNA leader.
D) Change in the rut binding site.
A) Change in the adenine-rich sequence of nucleotides of the terminator region.
Proteins are not always finished upon synthesis, often a mechanism is required to secrete, or
translocate the protein to its final destination to complete its folding, or function correctly. Elaborate
on one system that facilitates this.
Sec System: General secretion pathway [2pts]. Recognizes signal sequences within the protein to help
translocate a protein from the cytoplasm to the periplasm or external environment [3pts]
TAT System: folded protein secretion [2pts]. Recognizes “twin” arginine residues in the protein signal
sequence to direct a protein across the cytoplasmic (inner) membrane. [3pts]
Students may elaborate on specific secretion systems, i.e. the Type I-VI transport mechanisms. These will
be considered for grading.
Q1. Which of the following statements best explains why microbial geneticists initially focused on
regulation of gene expression at the transcriptional, rather than the translational, level?
A) By regulating the first step of protein synthesis, cells conserve the greatest amount of energy.
B) The process of transcription was best understood by researchers at the time.
C) Cellular regulation of transcription is common to all prokaryotic cells.
D) The process of synthesizing an mRNA transcript is much less complex than translation of
mRNA into protein.
A) By regulating the first step of protein synthesis, cells conserve the greatest amount of energy.
In the CRISPR/Cas system __________.
A) bacteria integrate portions of the viral genome into their own so they have a molecular
snapshot of their attacker to prevent future encounters
B) restriction endonucleases digest viral genomes once they enter the cell if the viral DNA is not
methylated
C) methylase enzymes add methyl groups to the viral nucleic acids, preventing transcription
D) methylated DNA sequences are hydrolyzed, effectively destroying the viral DNA
A) bacteria integrate portions of the viral genome into their own so they have a molecular
snapshot of their attacker to prevent future encounters
If Escherichia coli is cultured in broth containing both glucose and lactose, it _________.
A) uses glucose preferentially until the supply is exhausted, then uses lactose
B) uses lactose preferentially until the supply is exhausted, then uses glucose
C) uses glucose and lactose simultaneously
D) uses only the glucose (it cannot use lactose as a source of carbon)
A) uses glucose preferentially until the supply is exhausted, then uses lactose
Which of these is not a feature of Eukaryotic chromosomes?
A) Linear chromosomes
B) Histones
C) Multiple origins of replication
D) Monocistronic transcripts
E) Polycistronic transcripts
E
When considering archaea, they are generally regarded as_______
A) Having a bacteria-like RNA polymerase in a bacteria-like environment
B) Having a bacteria-like RNA polymerase in a Eukaryotic-like environment
C) Having a Eukaryotic-like RNA polymerase in a bacteria-like environment
D) Having a Eukaryotic-like RNA polymerase in a Eukaryotic-like environment
c
FR1. Give an example of what we would consider to be a “global regulatory system” and comment on
a specific contribution to a mechanism that ensures bacterial success.
- Two-component signal transduction systems: examples such as sensor/kinase systems that detect
an extracellular signal and initiate an intracellular response.
E.g. sensing attractants in chemotaxis to affect flagella rotation and subsequent motility, sensing
metabolites to trigger uptake systems, sensing oxygen to coordinate shifts in regulation of metabolic
pathways - Phosphorelay systems: Signaling systems wherein a regulatory cascade occurs through the
phosphorylation and dephosphorylation of a series of proteins, resulting in a final ‘effector’ able to elicit
change. E.g. chemotaxis system in motile bacteria impacting flagella rotation
** This answer may closely tie to 2-component systems. - Sigma factors: Crucial contributor to facilitating engagement of RNA polymerase with a gene, to initiae
transctiption. Different sigma factors have differing affinities for different DNA sequences, so alternate
sigma factors immediately change expression of many genes as they direct RNA polymerase to specific
subsets of bacterial promoters,
e.g. to change growth phase, metabolic modes, response to heat shock stress, etc - Second messengers: Small molecules produced in response to a signal (i.e. the first messenger) that is
outside the cell. Crucial component of signal transduction, and often tied to initiating a large scale/global
response to a trigger. Each responds to a particular type of environmental signal, and redirects cellular
physiology and gene expression to respond
e.g. catabolite repression, with CAP(CRP) interacting with cAMP to serve as an activator of the lac
operson when glucose levels are loww
By definition, if the DNA of a cell undergoes a spontaneous mutation, it was NOT due to _______.
A) errors in DNA replication
B) insertion of transposons
C) exposure to radiation
D) spontaneous depurination of nucleotides
c
Q2. Transition mutations can result from _________.
A) incorporation of a base analog that exhibits different base-pairing properties from the base it
replaces
B) chemical modification of an existing base in the DNA so that in the next round of replication it will pair
differently from the unmodified base
C) incorporation of a base analog that exhibits different base-pairing properties from the base it replaces
and chemical modification of an existing base in the DNA so that in the next round of replication it will
pair differently from the unmodified base
D) a small insertion or deletion
c
Which of the following types of mutation may play an important role in driving evolution because
they are often nonlethal and, therefore, remain in the gene pool?
A) Nonsense
B) Missense
C) Frameshift
D) Deletion
b
