USABO OPEN EXAM 2025 QUESTIONS
AND ANSWERS
Both amino acids and nucleotides form complex chains. Select all the answers below that are
accurate.
A. The chains formed by both have polar phosphate groups.
B. Both contain peptide bonds.
C. Both contain nitrogen.
D. The chains formed by both can be lysed by trypsin.
E. The sequence of chains both form from preexisting templates. - ANS C. Both contain
nitrogen.
E. The sequence of chains both form from preexisting templates.
When a population is in Hardy-Weinberg equilibrium, which of the following is true?
A. All of its recessive lethal genes are wiped out, leaving only healthy dominant genes.
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,B. dN/dt = 0, N = population size.
C. Mutations occur at five times the normal rate to balance the loss of genes by way of natural
selection.
D. The frequencies of the alleles in the population change over time.
E. The frequencies of genotypes in the population are stable over time. - ANS E. The
frequencies of genotypes in the population are stable over time.
Which of the following is NOT an accurate description of protein synthesis and folding?
A. All protein synthesis is initiated in the cytoplasm.
B. Many copies of a protein can be synthesized simultaneously from the same mRNA.
C. The 3D shape of a protein is determined largely by its amino acid sequence.
D. The entire chain of amino acids exits the ribosome before it begins folding into its 3D shape.
E. The first encoded amino acid in every protein is methionine. - ANS C. The 3D shape of a
protein is determined largely by its amino acid sequence.
Neurotransmitter released at the synapse binds to two classes of receptors. Select the correct
response(s).
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, A. Metabotropic receptors that do not form an ion pore are linked with signal transduction
mechanisms and can alter neuron function for seconds to minutes.
B. Receptor tyrosine kinases that activate signal transduction mechanisms and change gene
transcription that can last for hours to days.
C. Ionotropic receptors that do not form an ion pore are linked with signal transduction
mechanisms and can alter neuron function for seconds to minutes.
D. Ionotropic receptors that are directly linked to an ion pore and are opened within
milliseconds in response to neurotransmitter.
E. Steroid hormone receptors that can activate changes in gene transcription that can last for
hours to days. - ANS A. Metabotropic receptors that do not form an ion pore are linked with
signal transduction mechanisms and can alter neuron function for seconds to minutes.
D. Ionotropic receptors that are directly linked to an ion pore and are opened within
milliseconds in response to neurotransmitter.
Many proteins are transported around cells in vesicles. Which of the following determines the
specificity or directionality of vesicle transport?
A. Clathrin coat proteins.
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AND ANSWERS
Both amino acids and nucleotides form complex chains. Select all the answers below that are
accurate.
A. The chains formed by both have polar phosphate groups.
B. Both contain peptide bonds.
C. Both contain nitrogen.
D. The chains formed by both can be lysed by trypsin.
E. The sequence of chains both form from preexisting templates. - ANS C. Both contain
nitrogen.
E. The sequence of chains both form from preexisting templates.
When a population is in Hardy-Weinberg equilibrium, which of the following is true?
A. All of its recessive lethal genes are wiped out, leaving only healthy dominant genes.
Copyright ©2025 BRIGHTSTARS ALL RIGHTS RESERVED 1
,B. dN/dt = 0, N = population size.
C. Mutations occur at five times the normal rate to balance the loss of genes by way of natural
selection.
D. The frequencies of the alleles in the population change over time.
E. The frequencies of genotypes in the population are stable over time. - ANS E. The
frequencies of genotypes in the population are stable over time.
Which of the following is NOT an accurate description of protein synthesis and folding?
A. All protein synthesis is initiated in the cytoplasm.
B. Many copies of a protein can be synthesized simultaneously from the same mRNA.
C. The 3D shape of a protein is determined largely by its amino acid sequence.
D. The entire chain of amino acids exits the ribosome before it begins folding into its 3D shape.
E. The first encoded amino acid in every protein is methionine. - ANS C. The 3D shape of a
protein is determined largely by its amino acid sequence.
Neurotransmitter released at the synapse binds to two classes of receptors. Select the correct
response(s).
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, A. Metabotropic receptors that do not form an ion pore are linked with signal transduction
mechanisms and can alter neuron function for seconds to minutes.
B. Receptor tyrosine kinases that activate signal transduction mechanisms and change gene
transcription that can last for hours to days.
C. Ionotropic receptors that do not form an ion pore are linked with signal transduction
mechanisms and can alter neuron function for seconds to minutes.
D. Ionotropic receptors that are directly linked to an ion pore and are opened within
milliseconds in response to neurotransmitter.
E. Steroid hormone receptors that can activate changes in gene transcription that can last for
hours to days. - ANS A. Metabotropic receptors that do not form an ion pore are linked with
signal transduction mechanisms and can alter neuron function for seconds to minutes.
D. Ionotropic receptors that are directly linked to an ion pore and are opened within
milliseconds in response to neurotransmitter.
Many proteins are transported around cells in vesicles. Which of the following determines the
specificity or directionality of vesicle transport?
A. Clathrin coat proteins.
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