BSC 2005
Biological Sciences
Final Test Review
(Questions & Solutions)
2025
1
,1. A 15-year-old with familial hemiplegic migraine has a gain-of-
function mutation in CACNA1A. This mutation most directly affects
which process in neurons?
A. Voltage-gated P/Q-type calcium influx at presynaptic terminals
B. Sodium channel inactivation during action potentials
C. GABA receptor-mediated inhibition
D. Glutamate uptake by astrocytes
ANS: A
Rationale: CACNA1A encodes the α1A subunit of P/Q-type
voltage-gated Ca²⁺ channels responsible for presynaptic calcium
entry that triggers neurotransmitter release.
2. During hippocampal tetanic stimulation, an NMDA receptor
antagonist abolishes long-term potentiation (LTP). Which synaptic
event was prevented?
A. AMPA receptor phosphorylation
B. Ca²⁺ influx through NMDA channels
C. GABA release
D. Metabotropic glutamate receptor activation
ANS: B
Rationale: LTP induction requires postsynaptic Ca²⁺ entry through
NMDA receptors after Mg²⁺ block removal.
3. In a patch-clamp experiment on CA1 pyramidal neurons, glycine
application plus depolarization elicits an inward current at –65 mV
due to removal of Mg²⁺ block. This current is mediated by:
A. AMPA receptors
B. NMDA receptors
C. Kainate receptors
D. GABAA receptors
2
, ANS: B
Rationale: NMDA receptors require glycine co-agonist binding and
Mg²⁺ block relief to conduct inward cationic current.
4. A depressed patient’s serum BDNF levels are low. BDNF exerts its
trophic effects by binding to which receptor?
A. TrkB tyrosine kinase receptor
B. NMDA receptor
C. p75 neurotrophin receptor
D. GPR55
ANS: A
Rationale: BDNF preferentially activates the TrkB receptor,
promoting neuronal survival, growth, and synaptic plasticity.
5. In an optogenetic study, neurons expressing halorhodopsin
hyperpolarize under yellow light due to:
A. Chloride influx
B. Sodium influx
C. Calcium efflux
D. Proton influx
ANS: A
Rationale: Halorhodopsin is a light-activated chloride pump that
transports Cl⁻ into the cell, hyperpolarizing the membrane.
6. A subject carries the COMT Val¹⁵⁸Met polymorphism, reducing
enzyme activity. This genotype most likely leads to:
A. Increased prefrontal dopamine levels
B. Decreased norepinephrine catabolism
C. Enhanced serotonin reuptake
D. Reduced acetylcholine release
ANS: A
Rationale: COMT degrades catecholamines; lower activity
3
Biological Sciences
Final Test Review
(Questions & Solutions)
2025
1
,1. A 15-year-old with familial hemiplegic migraine has a gain-of-
function mutation in CACNA1A. This mutation most directly affects
which process in neurons?
A. Voltage-gated P/Q-type calcium influx at presynaptic terminals
B. Sodium channel inactivation during action potentials
C. GABA receptor-mediated inhibition
D. Glutamate uptake by astrocytes
ANS: A
Rationale: CACNA1A encodes the α1A subunit of P/Q-type
voltage-gated Ca²⁺ channels responsible for presynaptic calcium
entry that triggers neurotransmitter release.
2. During hippocampal tetanic stimulation, an NMDA receptor
antagonist abolishes long-term potentiation (LTP). Which synaptic
event was prevented?
A. AMPA receptor phosphorylation
B. Ca²⁺ influx through NMDA channels
C. GABA release
D. Metabotropic glutamate receptor activation
ANS: B
Rationale: LTP induction requires postsynaptic Ca²⁺ entry through
NMDA receptors after Mg²⁺ block removal.
3. In a patch-clamp experiment on CA1 pyramidal neurons, glycine
application plus depolarization elicits an inward current at –65 mV
due to removal of Mg²⁺ block. This current is mediated by:
A. AMPA receptors
B. NMDA receptors
C. Kainate receptors
D. GABAA receptors
2
, ANS: B
Rationale: NMDA receptors require glycine co-agonist binding and
Mg²⁺ block relief to conduct inward cationic current.
4. A depressed patient’s serum BDNF levels are low. BDNF exerts its
trophic effects by binding to which receptor?
A. TrkB tyrosine kinase receptor
B. NMDA receptor
C. p75 neurotrophin receptor
D. GPR55
ANS: A
Rationale: BDNF preferentially activates the TrkB receptor,
promoting neuronal survival, growth, and synaptic plasticity.
5. In an optogenetic study, neurons expressing halorhodopsin
hyperpolarize under yellow light due to:
A. Chloride influx
B. Sodium influx
C. Calcium efflux
D. Proton influx
ANS: A
Rationale: Halorhodopsin is a light-activated chloride pump that
transports Cl⁻ into the cell, hyperpolarizing the membrane.
6. A subject carries the COMT Val¹⁵⁸Met polymorphism, reducing
enzyme activity. This genotype most likely leads to:
A. Increased prefrontal dopamine levels
B. Decreased norepinephrine catabolism
C. Enhanced serotonin reuptake
D. Reduced acetylcholine release
ANS: A
Rationale: COMT degrades catecholamines; lower activity
3
