USABO Open Exam Questions with

USABO Open Exam Questions with Complete Solutions (Latest 2025) Why is myelin important in the nervous system?

• It allows signals to travel faster along axons because

depolarization occurs only at myelinated locations.

• It allows signals to travel faster along axons because

depolarization occurs only at nonmyelinated locations.

• It bundles the dendrites of adjacent neurons together.
• It increases capacitance across the cell membrane, which

helps electrical signals to leave the axons.

• It traps neurotransmitters, increasing their concentrations

in the synaptic cleft. - Correct Answers ✅B Which type of cytoskeletal fiber is the primary building block of eukaryotic cilia and flagella?

• Actin microfilaments.
• Intermediate filaments.
• Keratin.
• Microtubules.
• RNA. - Correct Answers ✅D. Microtubules.

Which of the following human cell types contains the LEAST amount of RNA involved in splicing? 1 / 3

USABO Open Exam Questions with Complete Solutions (Latest 2025)

• Lymphocytes
• Lymphoblasts
• Erythrocytes
• Erythroblasts
• Hepatocytes - Correct Answers ✅C. Erythrocytes

Antimicrobial drugs, also known as antibiotics, inhibit the growth of bacteria by targeting cellular components present in bacteria. Which of the following cellular components is NOT a valid antimicrobial drug target?

• Centrosome.
• Ribosome.
• Cell wall.
• RNA polymerase.
• DNA polymerase - Correct Answers ✅A. Centrosome.

Which of the following statements concerning the nature of post-transcriptional processing of mRNA is INCORRECT?

• The presence of introns is a derived trait of eukaryotes.
• Mitochondrial mRNA lacks a 5′ cap because capping is a

strictly intranuclear process. 2 / 3

USABO Open Exam Questions with Complete Solutions (Latest 2025)

• Recognition of splice sites by the spliceosome is based on

the physical conformation of the mRNA strand, not on any specific consensus sequence.

• In some genes, poly-A tails can generate genetic diversity

by being added at one of multiple possible sites on the mRNA transcript.

• Both 5′ caps and poly-A tails inhibit the degradation of the

mRNA molecule in the cytosol. - Correct Answers ✅C.Recognition of splice sites by the spliceosome is based on the physical conformation of the mRNA strand, not on any specific consensus sequence.Cellular metabolism is bidirectional and complex. Indicate whether the following statements concerning the metabolic capabilities of a nucleated human cell are True or False.

• Can convert sugars to fats
• Can convert fats to sugars
• Can convert sugars to amino acids
• Can convert amino acids to sugars - Correct Answers

✅A. True

• False
• True
• True
• / 3