1. During meiosis, when does crossing over occur and what is its significance?
Prophase I, contributing to genetic diversity.
Metaphase I, ensuring equal distribution of chromosomes.
Anaphase II, preventing nondisjunction.
Telophase II, facilitating chromosome separation.
Correct answer: A. Explanation: Crossing over occurs during prophase I of meiosis, where homologous chromosomes
exchange segments. This process contributes to genetic diversity by creating new combinations of genetic material.
2. In the Lac operon, what role does the repressor protein play when lactose is absent?
It binds to the operator, preventing transcription.
It enhances the binding of RNA polymerase to the promoter.
It undergoes a conformational change, allowing transcription.
It degrades lactose, preventing its use as an energy source.
Correct answer: A. Explanation: In the absence of lactose, the repressor protein binds to the operator region of the Lac
operon, blocking RNA polymerase and thus preventing transcription of the genes involved in lactose metabolism.
3. What role does the p53 gene play in cell cycle regulation?
It promotes the transition from G2 phase to M phase.
It functions as a tumor suppressor by initiating cell cycle arrest and apoptosis.
It enhances DNA replication in the S phase.
It facilitates cytokinesis during the M phase.
Correct answer: B. Explanation: The p53 gene is crucial for cell cycle regulation, acting as a tumor suppressor. When
DNA damage is detected, p53 can trigger cell cycle arrest, allowing for repair, or induce apoptosis if the damage is
irreparable.
4. In eukaryotic gene regulation, what role do enhancer sequences play?
They degrade mRNA to control gene expression.
They facilitate the binding of RNA polymerase to the promoter.
They act as binding sites for proteins that increase the likelihood of transcription.
They prevent transcription by binding repressor proteins.
Correct answer: C. Explanation: Enhancer sequences are regions of DNA that can bind transcription factors to increase
the likelihood of transcription of a particular gene, often by facilitating the assembly of the transcription machinery.
5. Which of the following best describes the function of the rough endoplasmic reticulum?
Synthesis and modification of lipids
Detoxification of drugs and poisons
Synthesis and processing of proteins
Packaging of proteins for secretion
Correct answer: C. Explanation: The rough endoplasmic reticulum is studded with ribosomes and is primarily involved in
the synthesis and processing of proteins that are either destined for the cell membrane, lysosomes, or for secretion.
6. Which of the following describes the role of the sodium-potassium pump during action potential generation
in neurons?
It pumps sodium ions out and potassium ions in, restoring the resting membrane potential.
, It pumps potassium ions out and sodium ions in, initiating depolarization.
It increases the permeability of the membrane to sodium ions, causing repolarization.
It decreases the permeability of the membrane to potassium ions, preventing hyperpolarization.
Correct answer: A. Explanation: The sodium-potassium pump helps maintain the resting membrane potential by
pumping three sodium ions out of the neuron and two potassium ions in. This action helps restore the ionic distribution
after an action potential, setting the stage for the next one.
7. What is the primary structure of a protein determined by?
Hydrogen bonding between amino acids
The sequence of amino acids
Disulfide bridges between cysteine residues
The alpha-helix and beta-sheet structures
Correct answer: B. Explanation: The primary structure of a protein is determined by its sequence of amino acids, which
dictates the subsequent folding and function of the protein.
8. In a eukaryotic cell, where does the Calvin cycle take place?
Mitochondrial matrix
Chloroplast stroma
Cytoplasm
Endoplasmic reticulum
Correct answer: B. Explanation: The Calvin cycle, part of the light-independent reactions of photosynthesis, occurs in
the stroma of chloroplasts. This is where carbon dioxide is fixed into organic molecules.
9. In the context of enzyme kinetics, what does the Michaelis-Menten constant (Km) indicate?
The maximum reaction speed at saturating substrate concentration.
The substrate concentration at which the reaction speed is half the maximum.
The rate at which an enzyme is degraded in the cell.
The affinity of an enzyme for its substrate at zero substrate concentration.
Correct answer: B. Explanation: The Michaelis-Menten constant (Km) is a measure of the substrate concentration at
which the reaction rate is half of its maximum value. It provides insight into the enzyme's affinity for its substrate: a lower
Km indicates higher affinity.
10. Which process is responsible for the independent assortment of alleles during gamete formation?
Synapsis during prophase I of meiosis
Random fertilization
Segregation during anaphase I of meiosis
Crossing over during prophase I of meiosis
Correct answer: C. Explanation: Independent assortment refers to the way chromosomes are randomly divided during
anaphase I of meiosis. This process leads to the formation of gametes with different combinations of alleles,
contributing to genetic diversity.
11. Which of the following best describes the relationship between photosynthesis and cellular respiration?
Photosynthesis occurs in animal cells, while cellular respiration occurs in plant cells.
The products of photosynthesis serve as the reactants in cellular respiration.
Cellular respiration produces glucose, which is then used in photosynthesis.
Photosynthesis and cellular respiration are unrelated processes.
, Correct answer: B. Explanation: Photosynthesis converts carbon dioxide and water into glucose and oxygen (products),
which are the reactants used in cellular respiration to produce energy in the form of ATP, along with carbon dioxide and
water as waste products.
12. What is the primary function of the Golgi apparatus in a cell?
Protein synthesis
ATP production
Modification, sorting, and packaging of proteins and lipids
Breakdown of cellular waste
Correct answer: C. Explanation: The Golgi apparatus is involved in the modification, sorting, and packaging of proteins
and lipids that have been synthesized in the cell, preparing them for their specific functions or transport out of the cell.
13. In a population adhering to Hardy-Weinberg equilibrium, what is true about the allele frequencies?
They change in response to natural selection.
They remain constant from one generation to the next in the absence of evolutionary influences.
They are not influenced by random mating.
They decrease with genetic drift.
Correct answer: B. Explanation: In a population in Hardy-Weinberg equilibrium, allele frequencies remain constant from
one generation to the next in the absence of evolutionary influences like natural selection, genetic drift, mutation, non-
random mating, and gene flow.
14. How does a competitive inhibitor affect enzyme activity?
It binds to the enzyme and changes its structure.
It increases the enzyme's affinity for the substrate.
It binds to the active site, preventing substrate binding.
It binds to a site other than the active site, changing the enzyme's shape.
Correct answer: C. Explanation: A competitive inhibitor competes with the substrate for binding to the active site of the
enzyme. When it binds, it prevents the substrate from binding, thus inhibiting the enzyme's activity.
15. Which reaction mechanism is typically involved in the formation of an ester from a carboxylic acid and an
alcohol?
E1
E2
SN1
SN2
Correct answer: C. Explanation: The formation of an ester from a carboxylic acid and an alcohol typically involves an
SN1 mechanism, where the carbonyl carbon of the acid is the electrophilic site attacked by the nucleophilic oxygen of
the alcohol.
16. What is the expected hybridization of the central atom in a molecule of XeF4?
sp
sp2
sp3
sp3d2
Correct answer: D. Explanation: In XeF4, the central atom xenon uses sp3d2 hybridization to form square planar
Prophase I, contributing to genetic diversity.
Metaphase I, ensuring equal distribution of chromosomes.
Anaphase II, preventing nondisjunction.
Telophase II, facilitating chromosome separation.
Correct answer: A. Explanation: Crossing over occurs during prophase I of meiosis, where homologous chromosomes
exchange segments. This process contributes to genetic diversity by creating new combinations of genetic material.
2. In the Lac operon, what role does the repressor protein play when lactose is absent?
It binds to the operator, preventing transcription.
It enhances the binding of RNA polymerase to the promoter.
It undergoes a conformational change, allowing transcription.
It degrades lactose, preventing its use as an energy source.
Correct answer: A. Explanation: In the absence of lactose, the repressor protein binds to the operator region of the Lac
operon, blocking RNA polymerase and thus preventing transcription of the genes involved in lactose metabolism.
3. What role does the p53 gene play in cell cycle regulation?
It promotes the transition from G2 phase to M phase.
It functions as a tumor suppressor by initiating cell cycle arrest and apoptosis.
It enhances DNA replication in the S phase.
It facilitates cytokinesis during the M phase.
Correct answer: B. Explanation: The p53 gene is crucial for cell cycle regulation, acting as a tumor suppressor. When
DNA damage is detected, p53 can trigger cell cycle arrest, allowing for repair, or induce apoptosis if the damage is
irreparable.
4. In eukaryotic gene regulation, what role do enhancer sequences play?
They degrade mRNA to control gene expression.
They facilitate the binding of RNA polymerase to the promoter.
They act as binding sites for proteins that increase the likelihood of transcription.
They prevent transcription by binding repressor proteins.
Correct answer: C. Explanation: Enhancer sequences are regions of DNA that can bind transcription factors to increase
the likelihood of transcription of a particular gene, often by facilitating the assembly of the transcription machinery.
5. Which of the following best describes the function of the rough endoplasmic reticulum?
Synthesis and modification of lipids
Detoxification of drugs and poisons
Synthesis and processing of proteins
Packaging of proteins for secretion
Correct answer: C. Explanation: The rough endoplasmic reticulum is studded with ribosomes and is primarily involved in
the synthesis and processing of proteins that are either destined for the cell membrane, lysosomes, or for secretion.
6. Which of the following describes the role of the sodium-potassium pump during action potential generation
in neurons?
It pumps sodium ions out and potassium ions in, restoring the resting membrane potential.
, It pumps potassium ions out and sodium ions in, initiating depolarization.
It increases the permeability of the membrane to sodium ions, causing repolarization.
It decreases the permeability of the membrane to potassium ions, preventing hyperpolarization.
Correct answer: A. Explanation: The sodium-potassium pump helps maintain the resting membrane potential by
pumping three sodium ions out of the neuron and two potassium ions in. This action helps restore the ionic distribution
after an action potential, setting the stage for the next one.
7. What is the primary structure of a protein determined by?
Hydrogen bonding between amino acids
The sequence of amino acids
Disulfide bridges between cysteine residues
The alpha-helix and beta-sheet structures
Correct answer: B. Explanation: The primary structure of a protein is determined by its sequence of amino acids, which
dictates the subsequent folding and function of the protein.
8. In a eukaryotic cell, where does the Calvin cycle take place?
Mitochondrial matrix
Chloroplast stroma
Cytoplasm
Endoplasmic reticulum
Correct answer: B. Explanation: The Calvin cycle, part of the light-independent reactions of photosynthesis, occurs in
the stroma of chloroplasts. This is where carbon dioxide is fixed into organic molecules.
9. In the context of enzyme kinetics, what does the Michaelis-Menten constant (Km) indicate?
The maximum reaction speed at saturating substrate concentration.
The substrate concentration at which the reaction speed is half the maximum.
The rate at which an enzyme is degraded in the cell.
The affinity of an enzyme for its substrate at zero substrate concentration.
Correct answer: B. Explanation: The Michaelis-Menten constant (Km) is a measure of the substrate concentration at
which the reaction rate is half of its maximum value. It provides insight into the enzyme's affinity for its substrate: a lower
Km indicates higher affinity.
10. Which process is responsible for the independent assortment of alleles during gamete formation?
Synapsis during prophase I of meiosis
Random fertilization
Segregation during anaphase I of meiosis
Crossing over during prophase I of meiosis
Correct answer: C. Explanation: Independent assortment refers to the way chromosomes are randomly divided during
anaphase I of meiosis. This process leads to the formation of gametes with different combinations of alleles,
contributing to genetic diversity.
11. Which of the following best describes the relationship between photosynthesis and cellular respiration?
Photosynthesis occurs in animal cells, while cellular respiration occurs in plant cells.
The products of photosynthesis serve as the reactants in cellular respiration.
Cellular respiration produces glucose, which is then used in photosynthesis.
Photosynthesis and cellular respiration are unrelated processes.
, Correct answer: B. Explanation: Photosynthesis converts carbon dioxide and water into glucose and oxygen (products),
which are the reactants used in cellular respiration to produce energy in the form of ATP, along with carbon dioxide and
water as waste products.
12. What is the primary function of the Golgi apparatus in a cell?
Protein synthesis
ATP production
Modification, sorting, and packaging of proteins and lipids
Breakdown of cellular waste
Correct answer: C. Explanation: The Golgi apparatus is involved in the modification, sorting, and packaging of proteins
and lipids that have been synthesized in the cell, preparing them for their specific functions or transport out of the cell.
13. In a population adhering to Hardy-Weinberg equilibrium, what is true about the allele frequencies?
They change in response to natural selection.
They remain constant from one generation to the next in the absence of evolutionary influences.
They are not influenced by random mating.
They decrease with genetic drift.
Correct answer: B. Explanation: In a population in Hardy-Weinberg equilibrium, allele frequencies remain constant from
one generation to the next in the absence of evolutionary influences like natural selection, genetic drift, mutation, non-
random mating, and gene flow.
14. How does a competitive inhibitor affect enzyme activity?
It binds to the enzyme and changes its structure.
It increases the enzyme's affinity for the substrate.
It binds to the active site, preventing substrate binding.
It binds to a site other than the active site, changing the enzyme's shape.
Correct answer: C. Explanation: A competitive inhibitor competes with the substrate for binding to the active site of the
enzyme. When it binds, it prevents the substrate from binding, thus inhibiting the enzyme's activity.
15. Which reaction mechanism is typically involved in the formation of an ester from a carboxylic acid and an
alcohol?
E1
E2
SN1
SN2
Correct answer: C. Explanation: The formation of an ester from a carboxylic acid and an alcohol typically involves an
SN1 mechanism, where the carbonyl carbon of the acid is the electrophilic site attacked by the nucleophilic oxygen of
the alcohol.
16. What is the expected hybridization of the central atom in a molecule of XeF4?
sp
sp2
sp3
sp3d2
Correct answer: D. Explanation: In XeF4, the central atom xenon uses sp3d2 hybridization to form square planar
