USABO OPEN EXAM QUESTIONS AND ANSWERS
Why is myelin important in the nervous system?
A. It allows signals to travel faster along axons because depolarization occurs only at
myelinated locations.
B. It allows signals to travel faster along axons because depolarization occurs only at
nonmyelinated locations.
C. It bundles the dendrites of adjacent neurons together.
D. It increases capacitance across the cell membrane, which helps electrical signals to
leave the axons.
E. It traps neurotransmitters, increasing their concentrations in the synaptic cleft. -
Answers :B
Which type of cytoskeletal fiber is the primary building block of eukaryotic cilia and
flagella?
A. Actin microfilaments.
B. Intermediate filaments.
C. Keratin.
D. Microtubules.
E. RNA. - Answers :D. Microtubules.
Consider the 5' to 3' nature of polymerase and its secondary functions and the structure
of a nucleotide and its incorporation into a growing polynucleotide chain. Select the best
possible explanation below for why evolution has favored 5' to 3' polymerases, as
opposed to 3' to 5' ones.
A. Binding of a 3' to 5' polymerase to DNA would be impaired.
B. The polymerase would not be able to conduct proofreading during the replication
process.
C. The active site of such a polymerase would be unable to incorporate the nucleotide
substrate.
D. The polynucleotide chain elongation reaction can only occur in a 5' to 3' manner.
E. None of the above. - Answers :B. The polymerase would not be able to conduct
proofreading during the replication process.
Some Archaea have structures called cannulae, which are hollow tubules made of
glycoprotein that connect cells. It is thought that the cannulae allow for the exchange of
nutrients and communication factors between archaeal cells. If this is so, which is the
closest analogue to cannulae from the list below?
A. Bacterial microtubules.
B. Archaeal hami.
C. Tight junctions in animal cells.
, D. Plasmodesmata in plant cells.
E. Animal microtubules. - Answers :D. Plasmodesmata in plant cells.
Which of the following is not a way for the cell to avoid accumulation of damaged and/or
malformed proteins?
A. Chaperonins.
B. Ubiquitination.
C. Nucleotide excision repair.
D. Proofreading DNA polymerases.
E. Dicer. - Answers :E. Dicer.
When a cell's DNA is damaged, it may develop into cancer when it divides. Which of the
following is most important in preventing development of cancer?
A. Cell division cycle (cdc) mutations.
B. Hypermutation in the p53 gene.
C. Kinetochore selectivity.
D. G1/S and G2/M checkpoints.
E. M checkpoint. - Answers :D. G1/S and G2/M checkpoints.
Syngenta Biotechnology introduced Golden Rice 2 to the public in 2005. This rice
variety has been genetically engineered to express a higher content of β-carotene. β-
carotene is important for vision and is a precursor to which vitamin?
A. Vitamin A.
B. Vitamin B.
C. Vitamin C.
D. Vitamin D.
E. Vitamin E. - Answers :A. Vitamin A.
Which of the following human cell types contains the LEAST amount of RNA involved in
splicing?
A. Lymphocytes
B. Lymphoblasts
C. Erythrocytes
D. Erythroblasts
E. Hepatocytes - 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?
A. Centrosome.
B. Ribosome.
Why is myelin important in the nervous system?
A. It allows signals to travel faster along axons because depolarization occurs only at
myelinated locations.
B. It allows signals to travel faster along axons because depolarization occurs only at
nonmyelinated locations.
C. It bundles the dendrites of adjacent neurons together.
D. It increases capacitance across the cell membrane, which helps electrical signals to
leave the axons.
E. It traps neurotransmitters, increasing their concentrations in the synaptic cleft. -
Answers :B
Which type of cytoskeletal fiber is the primary building block of eukaryotic cilia and
flagella?
A. Actin microfilaments.
B. Intermediate filaments.
C. Keratin.
D. Microtubules.
E. RNA. - Answers :D. Microtubules.
Consider the 5' to 3' nature of polymerase and its secondary functions and the structure
of a nucleotide and its incorporation into a growing polynucleotide chain. Select the best
possible explanation below for why evolution has favored 5' to 3' polymerases, as
opposed to 3' to 5' ones.
A. Binding of a 3' to 5' polymerase to DNA would be impaired.
B. The polymerase would not be able to conduct proofreading during the replication
process.
C. The active site of such a polymerase would be unable to incorporate the nucleotide
substrate.
D. The polynucleotide chain elongation reaction can only occur in a 5' to 3' manner.
E. None of the above. - Answers :B. The polymerase would not be able to conduct
proofreading during the replication process.
Some Archaea have structures called cannulae, which are hollow tubules made of
glycoprotein that connect cells. It is thought that the cannulae allow for the exchange of
nutrients and communication factors between archaeal cells. If this is so, which is the
closest analogue to cannulae from the list below?
A. Bacterial microtubules.
B. Archaeal hami.
C. Tight junctions in animal cells.
, D. Plasmodesmata in plant cells.
E. Animal microtubules. - Answers :D. Plasmodesmata in plant cells.
Which of the following is not a way for the cell to avoid accumulation of damaged and/or
malformed proteins?
A. Chaperonins.
B. Ubiquitination.
C. Nucleotide excision repair.
D. Proofreading DNA polymerases.
E. Dicer. - Answers :E. Dicer.
When a cell's DNA is damaged, it may develop into cancer when it divides. Which of the
following is most important in preventing development of cancer?
A. Cell division cycle (cdc) mutations.
B. Hypermutation in the p53 gene.
C. Kinetochore selectivity.
D. G1/S and G2/M checkpoints.
E. M checkpoint. - Answers :D. G1/S and G2/M checkpoints.
Syngenta Biotechnology introduced Golden Rice 2 to the public in 2005. This rice
variety has been genetically engineered to express a higher content of β-carotene. β-
carotene is important for vision and is a precursor to which vitamin?
A. Vitamin A.
B. Vitamin B.
C. Vitamin C.
D. Vitamin D.
E. Vitamin E. - Answers :A. Vitamin A.
Which of the following human cell types contains the LEAST amount of RNA involved in
splicing?
A. Lymphocytes
B. Lymphoblasts
C. Erythrocytes
D. Erythroblasts
E. Hepatocytes - 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?
A. Centrosome.
B. Ribosome.
