BCHM202 Final Exam 2025 / Verified Biochemistry Questions and Answers
Currently Testing | University of Maryland
Gene Expression-CORRECT ANSWER/S - Production of a protein that has an activity/function that creates a
trait in an organism.
Four types of regulation?-CORRECT ANSWER/S - 1. Changes in frequency of initiation of transcription
2. Changes in stability and/or structure of mRNA
3. Changes in frequency of translation initiation
4. Changes in the structure or processing of a protein.
Lac Operon-CORRECT ANSWER/S - An example of +ve and -ve transcriptional control.
A set of genes necessary for E.Coli to transport and metabolize lactose. In nature, only expressed when lactose
is present and glucose is absent.
Lactose-CORRECT ANSWER/S - 12 carbon sugar, composed of two 6 carbon sugars - galactose and glucose
(these 6C sugars will enter the Krebb's cycle to drive aerobic metabolism).
Beta-galactosidase-CORRECT ANSWER/S - Cleaves the bond between the two 6C sugars to create galactose
and glucose. It will also convert lactose into allolactose (which can also be further broken down into the 6C
sugars).
Lactose permease-CORRECT ANSWER/S - Transports lactose across the cell membrane into the cell so it can
be broken down. (6C sugars are only water soluble).
What two proteins distinguish E.Coli from other bacterium and allow E.Coli to use lactose as a carbon source?-
CORRECT ANSWER/S - Beta-galactosidase and lac permease.
Cis-acting elements-CORRECT ANSWER/S - DNA sequences that regulate gene expression and are located on
the same DNA molecule as the gene they control. Provide binding sites for proteins anad RNAs that regulate
transcription.
Trans-acting elements-CORRECT ANSWER/S - Molecules (usually proteins) that bind to cis-acting elements
to regulate gene expression, but can diffuse and act on different DNA molecules.
,Operator (LacO)-CORRECT ANSWER/S - DNA sequence to which the LacI gene product (the repressor) binds
Promoter-CORRECT ANSWER/S - Specific region of a gene where RNA polymerase can bind and begin
transcription. Contains conserved sequences like the -35 and -10 regions that RNA polymerase recognizes and
binds to.
Lac repressor-CORRECT ANSWER/S - Regulatory protein encoded by the LacI gene -> A protein that binds to
the operator site of the lac operon and inhibits transcription
In what condition will the lac repressor bind to the operator?-CORRECT ANSWER/S - In the absence of
lactose. Binds to the operator region and blocks RNA polymerase from transcribing lac genes.
Operator (lacO)-CORRECT ANSWER/S - DNA sequence within or near a gene's promoter that acts as a
regulatory "switch". lacO sits downstream of the promoter and upstream of the structural genes (lacZ, lacY,
lacA).
Basal level of transcription-CORRECT ANSWER/S - the interaction of general transcription factors and RNA
polymerase with the core promoter often initiates transcription at low rate.
constitutive expression-CORRECT ANSWER/S - Continuous gene expression regardless of environmental
conditions. (Same level of transcription)
What are the 3 different physiological states of lac operon transcription?-CORRECT ANSWER/S - - No lactose
in environment
- Little bit of lactose in environment
- All glucose gone, only lactose in environment
What happens in no lactose conditions?-CORRECT ANSWER/S - Both proteins are not produced, no
transcription. Lac-repressor is bound in the promoter region of those genes, preventing binding of RNA
polymerase.
, What happens in some lactose, some glucose conditions?-CORRECT ANSWER/S - Basal levels of
transcription/expression (No -ve or +ve control of the genes). Repressor stops binding the promoter. RNA
polymerase transcribes B-gal and lac permease.
What happens in conditions where all glucose is gone and only lactose is left?-CORRECT ANSWER/S -
Activator protein binds just upstream of the promoter to signal RNA polymerase to more efficiently initiate
transcription of the two proteins (ACTIVATED LEVEL).
Activator protein-CORRECT ANSWER/S - CAP (Catabolite activator protein) - Helps turn on transcription of
the lac operon when glucose is low. Binds to DNA upstream of lac promoter BUT only when cAMP is present.
CAP is a transcription factor.
Positive regulation-CORRECT ANSWER/S - Presence of regulatory protein (activator protein) at a regulatory
region promotes transcription. e.g. Lac operon -> Regulated by CAP and cyclic AMP.
Negative regulation-CORRECT ANSWER/S - Presence of regulatory protein (repressor) at a regulatory site
(operator) decreases mRNA synthesis.
Inducer-CORRECT ANSWER/S - Molecule that starts or increases gene expression by binding to a repressor,
inactivating it so transcription can proceed.
Co-repressor-CORRECT ANSWER/S - Molecule that helps turn OFF gene expression. Binds to a repressor
protein and activates it, enabling the repressor to bind to the operator and block transcription.
Global regulation-CORRECT ANSWER/S - Ability to control multiple genes or operons in response to overall
cellular conditions. Lac operon is not just controlled by the presence/absence of lactose but by the overall ability
of energy sources like glucose.
CAP-CORRECT ANSWER/S - Catabolite activator protein.
Binds to CAP site. Makes simultaneous contact with DNA sequence adjacent to the promoter and RNA
polymerase.
When bound, increases affinity of RNA polymerase for the promoter and lowers energy barrier to RNA pol.
unwinding the DNA molecule and initiating transcription.
Currently Testing | University of Maryland
Gene Expression-CORRECT ANSWER/S - Production of a protein that has an activity/function that creates a
trait in an organism.
Four types of regulation?-CORRECT ANSWER/S - 1. Changes in frequency of initiation of transcription
2. Changes in stability and/or structure of mRNA
3. Changes in frequency of translation initiation
4. Changes in the structure or processing of a protein.
Lac Operon-CORRECT ANSWER/S - An example of +ve and -ve transcriptional control.
A set of genes necessary for E.Coli to transport and metabolize lactose. In nature, only expressed when lactose
is present and glucose is absent.
Lactose-CORRECT ANSWER/S - 12 carbon sugar, composed of two 6 carbon sugars - galactose and glucose
(these 6C sugars will enter the Krebb's cycle to drive aerobic metabolism).
Beta-galactosidase-CORRECT ANSWER/S - Cleaves the bond between the two 6C sugars to create galactose
and glucose. It will also convert lactose into allolactose (which can also be further broken down into the 6C
sugars).
Lactose permease-CORRECT ANSWER/S - Transports lactose across the cell membrane into the cell so it can
be broken down. (6C sugars are only water soluble).
What two proteins distinguish E.Coli from other bacterium and allow E.Coli to use lactose as a carbon source?-
CORRECT ANSWER/S - Beta-galactosidase and lac permease.
Cis-acting elements-CORRECT ANSWER/S - DNA sequences that regulate gene expression and are located on
the same DNA molecule as the gene they control. Provide binding sites for proteins anad RNAs that regulate
transcription.
Trans-acting elements-CORRECT ANSWER/S - Molecules (usually proteins) that bind to cis-acting elements
to regulate gene expression, but can diffuse and act on different DNA molecules.
,Operator (LacO)-CORRECT ANSWER/S - DNA sequence to which the LacI gene product (the repressor) binds
Promoter-CORRECT ANSWER/S - Specific region of a gene where RNA polymerase can bind and begin
transcription. Contains conserved sequences like the -35 and -10 regions that RNA polymerase recognizes and
binds to.
Lac repressor-CORRECT ANSWER/S - Regulatory protein encoded by the LacI gene -> A protein that binds to
the operator site of the lac operon and inhibits transcription
In what condition will the lac repressor bind to the operator?-CORRECT ANSWER/S - In the absence of
lactose. Binds to the operator region and blocks RNA polymerase from transcribing lac genes.
Operator (lacO)-CORRECT ANSWER/S - DNA sequence within or near a gene's promoter that acts as a
regulatory "switch". lacO sits downstream of the promoter and upstream of the structural genes (lacZ, lacY,
lacA).
Basal level of transcription-CORRECT ANSWER/S - the interaction of general transcription factors and RNA
polymerase with the core promoter often initiates transcription at low rate.
constitutive expression-CORRECT ANSWER/S - Continuous gene expression regardless of environmental
conditions. (Same level of transcription)
What are the 3 different physiological states of lac operon transcription?-CORRECT ANSWER/S - - No lactose
in environment
- Little bit of lactose in environment
- All glucose gone, only lactose in environment
What happens in no lactose conditions?-CORRECT ANSWER/S - Both proteins are not produced, no
transcription. Lac-repressor is bound in the promoter region of those genes, preventing binding of RNA
polymerase.
, What happens in some lactose, some glucose conditions?-CORRECT ANSWER/S - Basal levels of
transcription/expression (No -ve or +ve control of the genes). Repressor stops binding the promoter. RNA
polymerase transcribes B-gal and lac permease.
What happens in conditions where all glucose is gone and only lactose is left?-CORRECT ANSWER/S -
Activator protein binds just upstream of the promoter to signal RNA polymerase to more efficiently initiate
transcription of the two proteins (ACTIVATED LEVEL).
Activator protein-CORRECT ANSWER/S - CAP (Catabolite activator protein) - Helps turn on transcription of
the lac operon when glucose is low. Binds to DNA upstream of lac promoter BUT only when cAMP is present.
CAP is a transcription factor.
Positive regulation-CORRECT ANSWER/S - Presence of regulatory protein (activator protein) at a regulatory
region promotes transcription. e.g. Lac operon -> Regulated by CAP and cyclic AMP.
Negative regulation-CORRECT ANSWER/S - Presence of regulatory protein (repressor) at a regulatory site
(operator) decreases mRNA synthesis.
Inducer-CORRECT ANSWER/S - Molecule that starts or increases gene expression by binding to a repressor,
inactivating it so transcription can proceed.
Co-repressor-CORRECT ANSWER/S - Molecule that helps turn OFF gene expression. Binds to a repressor
protein and activates it, enabling the repressor to bind to the operator and block transcription.
Global regulation-CORRECT ANSWER/S - Ability to control multiple genes or operons in response to overall
cellular conditions. Lac operon is not just controlled by the presence/absence of lactose but by the overall ability
of energy sources like glucose.
CAP-CORRECT ANSWER/S - Catabolite activator protein.
Binds to CAP site. Makes simultaneous contact with DNA sequence adjacent to the promoter and RNA
polymerase.
When bound, increases affinity of RNA polymerase for the promoter and lowers energy barrier to RNA pol.
unwinding the DNA molecule and initiating transcription.
