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USABO Open Exam 2009
USABO Open Exam 2009
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USABO Open Exam 2009Sunflower chromosomes have been isolated and their DNA/NT analyzed. It was found that
chromosome 2 has unusually high content of Adenine (40%). How many percent of Guanine
is present in chromosome 2?
A. 10%
B. 20%
C. 30%
D. 40 %
E. 50% - correct answer-A. 10%
Sunflower chromosomes have been isolated and their DNA/NT analyzed. It was found that
chromosome 2 has unusually high content of Adenine (40%). Assume that the entire
sequence of the chromosome is transcribed. Which of the following is true for the content of
Adenine in the transcribed RNA?
A. Adenine is 40% of the RNA.
B. Adenine is 20% of the RNA.
C. Adenine is at least 20% of the RNA.
D. Adenine is at least 40% of the RNA.
E. The content of Adenine is not possible to determine based on the information provided. -
correct answer-E. The content of Adenine is not possible to determine based on the
information provided.
Which of the following is a primary organ or structure of the immune system?
A. Spleen
B. Thymus
C. Tonsils
D. Lymph nodes
E. Appendix - correct answer-B. Thymus
"Hairs" (such as trichomes) on the surface of leaves may limit:
A. photosynthesis.
B. intake of carbon dioxide.
C. evapotranspiration.
D. drought adaptations.
E. movement of water in the vessels. - correct answer-C. evapotranspiration.
You discover a worm-like organism that inhabits soil samples that has the following
characteristics: segmented body and few bristle-like extensions. To which one of the
following groups will you assign this organism?
A. Cestoda
, B. Polychaeta
C. Oligochatea
D. Onychophora
E. Myriapoda - correct answer-C. Oligochatea
Evolution is a product of:
A. realized niche and biomagnification.
B. phenotypic variation and selective pressures.
C. rainfall and temperature.
D. adaptability within one generation.
E. extinction and landscape variability. - correct answer-B. phenotypic variation and selective
pressures.
Which of the following is NOT true of allosterically regulated enzymes?
A. Their activity can be modulated by effector molecules.
B. They demonstrate cooperativity.
C. Their activity can be modulated by substrate concentration.
D. They follow Michaelis-Menten kinetics. E. Plots of their rate of product formation versus
substrate concentration are sigmoidal in shape. - correct answer-D. They follow
Michaelis-Menten kinetics. E. Plots of their rate of product formation versus substrate
concentration are sigmoidal in shape.
Why can glycolysis proceed under anaerobic or aerobic conditions while the citric acid cycle
only proceeds under aerobic conditions?
A. Oxygen is a byproduct of the conversion of the glycolytic intermediate
glucose-6-phosphate to fructose-6-phosphate.
B. Enzymes of glycolysis do not use oxygen as cofactors, while enzymes of the citric acid
cycle require oxygen for proper folding.
C. Enzyme catalysis during the citric acid cycle is regulated by allosteric effectors, which
include oxygen.
D. NAD+ is produced during three steps of glycolysis and only one step of the citric acid
cycle.
E. Under anaerobic conditions, NAD+ (for glycolysis) can be regenerated through the
conversion of pyruvate into lactate. - correct answer-E. Under anaerobic conditions, NAD+
(for glycolysis) can be regenerated through the conversion of pyruvate into lactate.
If a child is blood type O, which of the following blood types is IMPOSSIBLE for either
parent?
A. A
B. B
C. O
D. AB
E. None are impossible - correct answer-D. AB
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