BS 161 EXAM 4 QUESTIONS WITH CORRECT ANSWERS LATEST UPDATE 2025/2026
A new nucleotide can only be added to the _____ end of a growing DNA strand. DNA therefore
always grows in the _____ direction. - Answers 3'; 5' to 3'
If you were able to find a drug that could inhibit the reactivation of telomerase activity in cancer
cells, the cancer cells would: - Answers slowly erode their chromosome ends.
Which of the reasons explains why bacteria can continually divide while they maintain the length
of their chromosome? - Answers because their DNA is circular, it never shortens after
replication
When we say that DNA replication is semiconservative, we mean that: - Answers when DNA is
replicated each new double helix contains one parental strand and one newly synthesized
daughter strand
As a piece of linear DNA is replicated, the leading strand will have _____ RNA primer(s) and the
lagging strand will have _____ RNA primer(s). - Answers one; many
A lack of telomerase activity limits what? - Answers the number of times a cell can divide
In eukaryotes, initiation of translation of a messenger RNA is determined in part by: - Answers
whether or not the 5′ cap on the mRNA is present.
Gene regulation by means of epigenetic mechanisms is useful to the organism because it: -
Answers can differ between the sexes, does not require new mutations, can respond rapidly too
environmental change, can quickly be reversed.
RNA processing occurs in the: - Answers nucleus.
In eukaryotes, the messenger RNA consists of: - Answers an RNA transcript with cap added,
introns removed, and poly(A) sequence added.
The process by which a single primary RNA transcript is used to make multiple proteins is
called: - Answers alternative splicing.
Insulin is needed to regulate sugar levels in the blood. While every cell in the body contains
genes to produce insulin, it is only produced by a specialized subset of cells in the pancreas.
Therefore: - Answers mechanisms of gene regulation promote insulin expression in the
specialized pancreatic cells and prevent insulin expression in all other cells
A loss of function mutation in which labeled sequence in the diagram would likely result in
continuous production of the enzymes from the lac operon? - Answers lacI
The trp operon is subject to negative regulation. This means that: - Answers the genes in the
operon are being transcribed until the repressor protein binds
, In the lactose operon of E. coli, the product of the lacI gene is a(n) _____ of transcription. -
Answers negative regulator
In the lactose operon of E. coli, what would happen if there was a mutation in the lacP promoter
that stopped proteins from binding to the promoter? - Answers the genes would not be
transcribed
In lac operon regulation, how many proteins are bound to DNA when E. coli is grown in medium
containing NEITHER glucose nor lactose? - Answers Both CRP and the lac repressor are bound
to the DNA.
In lac operon regulation, how many proteins are bound to DNA when E. coli is grown in medium
containing both glucose and lactose? - Answers Neither CRP nor the lac repressor is bound to
the DNA.
What organism produced the synthetic insulin described in the articles? - Answers e coli
Why do you think that a bacterial promoter is required to express a human gene in bacteria? -
Answers The human promoter sequence is not recognized by bacterial RNA polymerase.
The lac operon is under positive control by the CRP-cAMP complex. In order for the operon to be
transcribed at a high level, what must happen? Select all that apply. - Answers cAMP is at high
concentration. cAMP-CRP is bound to the regulatory region of the operon.
The promoter for the lac operon has a low affinity for RNA polymerase and the promoter for the
lacI repressor protein has a high affinity for RNA polymerase. - Answers true
The lacZ and lacY genes are transcribed when: - Answers lactose is present and glucose levels
are low.
What will the effect be of a mutation that disrupts the promoter sequence in the lactose operon?
- Answers the structural genes will never be transcribed.
In E. coli, the production of lac repressor is constitutive. - Answers true
In prokaryotes: - Answers the translation of an mRNA can begin even before transcription is
completed.
An operon is a: - Answers region of DNA consisting of the promoter, the operator, and coding
sequences for structural proteins.
What determines what types of food a bacterium can use as an energy source? - Answers The
types of enzymes found in the bacterium.
What is the process of "proofreading" by DNA polymerase - Answers removing an improperly
paired base and replacing it with the proper one
A new nucleotide can only be added to the _____ end of a growing DNA strand. DNA therefore
always grows in the _____ direction. - Answers 3'; 5' to 3'
If you were able to find a drug that could inhibit the reactivation of telomerase activity in cancer
cells, the cancer cells would: - Answers slowly erode their chromosome ends.
Which of the reasons explains why bacteria can continually divide while they maintain the length
of their chromosome? - Answers because their DNA is circular, it never shortens after
replication
When we say that DNA replication is semiconservative, we mean that: - Answers when DNA is
replicated each new double helix contains one parental strand and one newly synthesized
daughter strand
As a piece of linear DNA is replicated, the leading strand will have _____ RNA primer(s) and the
lagging strand will have _____ RNA primer(s). - Answers one; many
A lack of telomerase activity limits what? - Answers the number of times a cell can divide
In eukaryotes, initiation of translation of a messenger RNA is determined in part by: - Answers
whether or not the 5′ cap on the mRNA is present.
Gene regulation by means of epigenetic mechanisms is useful to the organism because it: -
Answers can differ between the sexes, does not require new mutations, can respond rapidly too
environmental change, can quickly be reversed.
RNA processing occurs in the: - Answers nucleus.
In eukaryotes, the messenger RNA consists of: - Answers an RNA transcript with cap added,
introns removed, and poly(A) sequence added.
The process by which a single primary RNA transcript is used to make multiple proteins is
called: - Answers alternative splicing.
Insulin is needed to regulate sugar levels in the blood. While every cell in the body contains
genes to produce insulin, it is only produced by a specialized subset of cells in the pancreas.
Therefore: - Answers mechanisms of gene regulation promote insulin expression in the
specialized pancreatic cells and prevent insulin expression in all other cells
A loss of function mutation in which labeled sequence in the diagram would likely result in
continuous production of the enzymes from the lac operon? - Answers lacI
The trp operon is subject to negative regulation. This means that: - Answers the genes in the
operon are being transcribed until the repressor protein binds
, In the lactose operon of E. coli, the product of the lacI gene is a(n) _____ of transcription. -
Answers negative regulator
In the lactose operon of E. coli, what would happen if there was a mutation in the lacP promoter
that stopped proteins from binding to the promoter? - Answers the genes would not be
transcribed
In lac operon regulation, how many proteins are bound to DNA when E. coli is grown in medium
containing NEITHER glucose nor lactose? - Answers Both CRP and the lac repressor are bound
to the DNA.
In lac operon regulation, how many proteins are bound to DNA when E. coli is grown in medium
containing both glucose and lactose? - Answers Neither CRP nor the lac repressor is bound to
the DNA.
What organism produced the synthetic insulin described in the articles? - Answers e coli
Why do you think that a bacterial promoter is required to express a human gene in bacteria? -
Answers The human promoter sequence is not recognized by bacterial RNA polymerase.
The lac operon is under positive control by the CRP-cAMP complex. In order for the operon to be
transcribed at a high level, what must happen? Select all that apply. - Answers cAMP is at high
concentration. cAMP-CRP is bound to the regulatory region of the operon.
The promoter for the lac operon has a low affinity for RNA polymerase and the promoter for the
lacI repressor protein has a high affinity for RNA polymerase. - Answers true
The lacZ and lacY genes are transcribed when: - Answers lactose is present and glucose levels
are low.
What will the effect be of a mutation that disrupts the promoter sequence in the lactose operon?
- Answers the structural genes will never be transcribed.
In E. coli, the production of lac repressor is constitutive. - Answers true
In prokaryotes: - Answers the translation of an mRNA can begin even before transcription is
completed.
An operon is a: - Answers region of DNA consisting of the promoter, the operator, and coding
sequences for structural proteins.
What determines what types of food a bacterium can use as an energy source? - Answers The
types of enzymes found in the bacterium.
What is the process of "proofreading" by DNA polymerase - Answers removing an improperly
paired base and replacing it with the proper one
