USABO Open Exam Questions
and Complete Solutions
Graded A+
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. - Answer: 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.
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. - Answer: 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. - Answer: 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).
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. - Answer: 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.
B. v-SNARES and t-SNARES.
C. Flippase.
D. Myristoylation.
E. Hydrophobic domains. - Answer: B. v-SNARES and t-SNARES.
The primary energy source of the brain is
A. Arabinose.
, B. Creatine.
C. Fructose.
D. Glucose.
E. L-serine. - Answer: D. Glucose.
Which set of the following statements are correct?
1. Osmosis can be used to measure the molecular weight of macromolecules.
2. Aquaporins affect the rate of water transport across membranes.
3. Antidiuretic hormone (ADH) controls aquaporins and the reabsorption of water in the kidney.
4. Reverse osmosis is a process that uses a pressure greater than the osmotic pressure to force the
solvent through a semi-permeable membrane from the side with a high solute concentration.
5. Passive proton pumps in plant cell membranes establish proton gradients.
A. Only statements 2, 3 & 4 are correct.
B. Only statements 5, 2 & 3 are correct.
C. Only statements 1, 2 & 3 are correct.
D. Only statements 1, 2, 3, & 4 are correct.
E. All statements are correct. - Answer: D. Only statements 1, 2, 3, & 4 are correct.
If two animals with the genotype AaBb X AaBb are mated, what is the probability of generating an
offspring with the genotype AABb? Assume there is no linkage between the two genes.
A. 1/8
B. 1/4
C. 3/8
D. 1/2
E. 5/8 - Answer: A. 1/8
Glycogenesis and glycogenolysis are controlled primarily by two hormones.
and Complete Solutions
Graded A+
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. - Answer: 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.
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. - Answer: 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. - Answer: 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).
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. - Answer: 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.
B. v-SNARES and t-SNARES.
C. Flippase.
D. Myristoylation.
E. Hydrophobic domains. - Answer: B. v-SNARES and t-SNARES.
The primary energy source of the brain is
A. Arabinose.
, B. Creatine.
C. Fructose.
D. Glucose.
E. L-serine. - Answer: D. Glucose.
Which set of the following statements are correct?
1. Osmosis can be used to measure the molecular weight of macromolecules.
2. Aquaporins affect the rate of water transport across membranes.
3. Antidiuretic hormone (ADH) controls aquaporins and the reabsorption of water in the kidney.
4. Reverse osmosis is a process that uses a pressure greater than the osmotic pressure to force the
solvent through a semi-permeable membrane from the side with a high solute concentration.
5. Passive proton pumps in plant cell membranes establish proton gradients.
A. Only statements 2, 3 & 4 are correct.
B. Only statements 5, 2 & 3 are correct.
C. Only statements 1, 2 & 3 are correct.
D. Only statements 1, 2, 3, & 4 are correct.
E. All statements are correct. - Answer: D. Only statements 1, 2, 3, & 4 are correct.
If two animals with the genotype AaBb X AaBb are mated, what is the probability of generating an
offspring with the genotype AABb? Assume there is no linkage between the two genes.
A. 1/8
B. 1/4
C. 3/8
D. 1/2
E. 5/8 - Answer: A. 1/8
Glycogenesis and glycogenolysis are controlled primarily by two hormones.
