USABO Open Exam Questions with

USABO Open Exam Questions with Complete Solutions (Latest 2025) Both amino acids and nucleotides form complex chains.Select all the answers below that are accurate.

• The chains formed by both have polar phosphate groups.
• Both contain peptide bonds.
• Both contain nitrogen.
• The chains formed by both can be lysed by trypsin.
• The sequence of chains both form from preexisting

templates. - Correct Answers ✅C. Both contain nitrogen.

• The sequence of chains both form from preexisting

templates.When a population is in Hardy-Weinberg equilibrium, which of the following is true?

• All of its recessive lethal genes are wiped out, leaving only

healthy dominant genes.

• dN/dt = 0, N = population size.
• Mutations occur at five times the normal rate to balance

the loss of genes by way of natural selection.

• The frequencies of the alleles in the population change

over time.

• The frequencies of genotypes in the population are stable

over time. - Correct Answers ✅E. The frequencies of genotypes in the population are stable over time. 1 / 3

USABO Open Exam Questions with Complete Solutions (Latest 2025) Which of the following is NOT an accurate description of protein synthesis and folding?

• All protein synthesis is initiated in the cytoplasm.
• Many copies of a protein can be synthesized

simultaneously from the same mRNA.

• The 3D shape of a protein is determined largely by its

amino acid sequence.

• The entire chain of amino acids exits the ribosome before

it begins folding into its 3D shape.

• The first encoded amino acid in every protein is

methionine. - Correct Answers ✅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).

• Metabotropic receptors that do not form an ion pore are

linked with signal transduction mechanisms and can alter neuron function for seconds to minutes.

• Receptor tyrosine kinases that activate signal transduction

mechanisms and change gene transcription that can last for hours to days. 2 / 3

USABO Open Exam Questions with Complete Solutions (Latest 2025)

• Ionotropic receptors that do not form an ion pore are linked

with signal transduction mechanisms and can alter neuron function for seconds to minutes.

• Ionotropic receptors that are directly linked to an ion pore

and are opened within milliseconds in response to neurotransmitter.

• Steroid hormone receptors that can activate changes in

gene transcription that can last for hours to days. - Correct Answers ✅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.

• 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?

• Clathrin coat proteins.
• v-SNARES and t-SNARES.
• Flippase.
• Myristoylation.
• Hydrophobic domains. - Correct Answers ✅B. v-SNARES

and t-SNARES.

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