BIOCHEMISTRY-LE-8 (2025) Flashcards
- In the context of a prokaryotic gene expression which of the following is the most appropriate definition of an operator?
A. a cluster of genes that are regulated by a single promoter
B. a DNA binding protein that regulates gene expression
C. a non-coding regulatory DNA sequence that is bound by RNA
D. a non-coding regulatory DNA sequence that is bound by a repressor protein
D. a non-coding regulatory DNA sequence that is bound by a repressor protein
- In terms of lac operon regulation, what happens when E. coli is grown in medium containing glucose and lactose?
A. both CAP and the lac repressor are bound to the DNA
B. CAP is bound to the DNA but the lac repressor is not
C. Lac repressor is bound to the DNA but CAP is not
D. Neither CAP nor the lac repressor gene are bound to the DNA
D. Neither CAP nor the lac repressor gene are bound to the DNA
- Nuclear Receptors belong to what class of transcription factor?
A. Helix loop helix proteins
B. Helix turn helix proteins
C. Leucine zipper proteins
D. Zinc finger proteins
D. Zinc finger proteins
- Which of the following statements regarding the regulation of trp operon expression by attenuation is correct?
A. The leader peptide sequence encodes
enzymes related to tryptophan
synthesis
B. The leader peptide sequence contains
no tryptophan residues
C. Rapid translation of the leader peptide
allows completion of the mRNA transcript
D. Rapid translation of the leader peptide prevents completion of the mRNA transcript
D. Rapid translation of the leader peptide prevents completion of the mRNA transcript
- RNAi stands for which of the following?
A. RNA inducer
B. RNA insertion
C. RNA interference
D. RNA intron
C. RNA interference
- Which of the following is true of the lac operon in E. Coli?
A. The operon is only switched on in the
absence of lactose in the growth
medium
B. The lac operon messenger RNA is a polycistronic mRNA
C. The enzyme B galactosidase is only produced in large quantities when the lac repressor is bound to the operator
D. The promoter is the binding site for the lac repressor
B. The lac operon messenger RNA is a polycistronic mRNA
- Which of the following statements about mRNA stability is correct?
A. Eukaryotic mRNAs have a half life of
only a few minutes
B. Regulation of mRNA stability is a way of regulating gene expression
C. It is thought that poly A tails stabilize prokaryotic RNAs
D. Histone mRNAs have especially long polyA tails and are especially stable
B. Regulation of mRNA stability is a way of regulating gene expression
- An epigenetic change in gene expression is an inherited change that does not involve any change in the nucleotide sequence of the gene.
A. True
B. False
A. True
- Which of the following statements is true
of RNA interference?
A. is a normal way for organisms to regulate gene expression
B. is a mechanism for combating virus infection in plants
C. occurs only in vertebrates
D. is already used therapeutically in
many disorders
A. is a normal way for organisms to regulate gene expression
- Identify the figure on the right:
A. acetylated histones
B. unacetylated histones
C. DNA methylation
D. RNA methylation
A. acetylated histones
- Gene regulation in bacteria os important in order to:
A. prevent wasting energy
B. enable response to environmental
stimuli
C. allow cells to adjust promptly to
changes in the growth medium
D. all of the above
D. all of the above
- Examples of internal stimuli originating from within the organism that coordinate gene expression include all of the following except:
A. steroid hormone
B. growth factors
C. sunlight
D. HSP70
C. sunlight
- Which statement is incorrect?
A. Gene regulation is fundamental to cell
specialization in multicellular
organisms
B. Patterns of gene expression established during the early developmental stages are not permanent, enabling one cell type to differentiate in a different cell
type later in the life cycle
C. Some gene family members are expressed at different phases of development
D. Post transcriptional and post translational processing events can regulate the synthesis rate of gene products.
B. Patterns of gene expression established during the early developmental stages are not permanent, enabling one cell type to differentiate in a different cell
type later in the life cycle
Which among the following statements is true regarding an operon?
A. cluster of genes transcribed by
multiple mRNA
B. gene transcription is prevented by the blocking of RNA polymerase
C. genes for multiple genetic pathways
D. can be switched off by a corepressor
B. gene transcription is prevented by the blocking of RNA polymerase
Which of the following is correctly matched?
A. Lactose: glucose and fructose
subunits
B. lacl: structural gene
C. operon: one promoter transcribes
more than one gene as a single
mRNA molecule
D. permease: transports lactose to the outside of the cell
C. operon: one promoter transcribes
more than one gene as a single
mRNA molecule
Proteins to be degraded are tagged with:
A. hydroquinone
B. ubiquitin
C. proteasome
D. allolactose
B. ubiquitin
An example of cleavage modification in eukaryotes is:
A. Crystallin Gene
B. preproinsulin
C. acetylation
D. methylation
B. preproinsulin
. The location where the lactose repressor gene binds to the lactose operon is called:
A. operator
B. promoter
C. inducer
D. enhancer
A. operator
When the lactose repressor is bound to the lactose operon:
A. lactose but not glucose metabolism
occurs
B. the transcription of lacl is blocked
C. access to the promoter by RNA
polymerase is blocked and transcription of the operon does not occur
D. the repressor is unable to bind to its allolactose
C. access to the promoter by RNA
polymerase is blocked and transcription of the operon does not occur
If lactose and glucose are both provided in the growth medium:
A. both lactose and glucose are
metabolized at similar rates
B. the lactose operon is not transcribed
C. lactose metabolism is favored
D. elevated levels of CAMP are
synthesized
B. the lactose operon is not transcribed
This type of mutation may have no detectable effect because of the degeneracy of the genetic code
A. Silent mutations
B. Missense mutations
C. Nonsense mutations
D. Frameshift mutations
A. Silent mutations
The type of mutation that alters gametes and are passed to the next generation
A. Somatic mutations
B. Missense mutations
C. Germline mutations
D. Frameshift mutations
C. Germline mutations
This type of mutation would be more likely to occur if the changed base in the mRNA molecule were to be at the third nucleotide of a codon.
A. Silent mutations
B. Missense mutations
C. Nonsense mutations
D. Frameshift mutations
A. Silent mutations
Because of wobble, the translation of a codon is least sensitive to a change at which position?
A. first
B. second
C. third
D. any position
C. third
A mutation may appear that would then result in the premature termination of amino acid incorporation into a peptide chain and the production of only a fragment of the intended protein molecule.
A. Silent mutations
B. Missense mutations
C. Nonsense mutations
D. Frameshift mutation
C. Nonsense mutations
The type of mutation that occur in somatic cells and only affect the individual in which the mutation arises
A. Somatic mutations
B. Missense mutations
C. Germline mutations
D. Frameshift mutations
A. Somatic mutations
The end product of this mutation has a high probability that a prematurely terminated protein molecule or peptide fragment will not function in its assigned role
A. Silent mutations
B. Missense mutations
C. Nonsense mutations
D. Frameshift mutations
C. Nonsense mutations
- The effect of this mutation will occur when a different amino acid is incorporated at the corresponding site in the protein molecule
A. Silent mutations
B. Missense mutations
C. Nonsense mutations
D. Frameshift mutation
B. Missense mutations
This mutation result from deletion or insertion of nucleotides in DNA that generates altered mRNAs
A. Silent mutations
B. Missense mutations
C. Nonsense mutations
D. Frameshift mutations
B. Missense mutations
The mRNA is read continuously from a start codon to a termination codon. Which among the following is a start codon?
A. AUG
B. UAA
C. UAG
D. UGA
A. AUG
Exposure of a cell to this agent can result in the covalent joining of two adjacent pyrimidines (usually thymines), producing a dimer.
A. X-rays
B. UV light
C. Base analogs
D. Alkylating agents
B. UV light
Exposure to this agent can cause double- strand breaks in DNA, which are potentially lethal to the cell
A. High-energy radiation
B. Base analogs
C. Alkylating agents
D. Viruses
A. High-energy radiation
This is another agent that can cause double- strand breaks in DNA that is potentially lethal to the cell
A. 5-bromouracil
B. oxidative free radicals
C. Alkylating agents
D. Hydroxylating agents
B. oxidative free radicals
A type of base pair substitution that converts a purine-pyrimidine to the other purine-pyrimidine
A. Transition
B. Base analogs
C. Transversions
D. Viruses
A. Transition
A type of base pair substitution that converts purine-pyrimidine to a pyrimidine-purine
A. Transition
B. Base analogs
C. Transversions
D. Viruses
C. Transversions
A type of base pair substitution that are more likely to result in nonsynonomous substitution
A. Transition
B. Base analogs
C. Transversions
D. Viruses
C. Transversions
A type of mutation wherein a base pair substitution results in substitution of an amino acid with similar chemical properties (protein function is not altered)
A. Neutral nonsynonymous mutation
B . Silent mutations
C. Nonsense mutations
D. Frameshift mutations
A. Neutral nonsynonymous mutation
A type of mutation which changes wild type (ancestral) to mutant (derived) gene
A. Neutral nonsynonymous mutation
B. Silent mutations
C. Reverse mutation
D. Forward mutation
D. Forward mutation
A type of mutation which changes mutant (derived) to wild type (ancestral) gene
A. Neutral nonsynonymous mutation
B. Silent mutations
C. Reverse mutation
D. Forward mutation
C. Reverse mutation
A type of spontaneous mutation wherein A or G are removed and replaced with a random base
A. Neutral nonsynonymous mutation
B. Silent mutations
C. Depurination
D. Deamination
C. Depurination