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USABO Open Exam Questions And Answers.
Question 1: Sunflower 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%
Question 2: 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?
- Adenine is 40% of the RNA.
- Adenine is 20% of the RNA.
- Adenine is at least 20% of the RNA.
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- Adenine is at least 40% of the RNA.
- 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.
Question 3: Which of the following is a primary organ or
structure of the immune system?
- Spleen
- Thymus
- Tonsils
- Lymph nodes
- Appendix
CORRECT ANSWER : B. Thymus
Question 4: "Hairs" (such as trichomes) on the surface of leaves
may limit:
- photosynthesis.
- intake of carbon dioxide.
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- evapotranspiration.
- drought adaptations.
- movement of water in the vessels.
CORRECT ANSWER : C. evapotranspiration.
Question 5: 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?
- Cestoda
- Polychaeta
- Oligochatea
- Onychophora
- Myriapoda
CORRECT ANSWER : C. Oligochatea
Question 6: Evolution is a product of:
- realized niche and biomagnification.
- phenotypic variation and selective pressures.
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- rainfall and temperature.
- adaptability within one generation.
- extinction and landscape variability.
CORRECT ANSWER : B. phenotypic variation and selective
pressures.
Question 7: Which of the following is NOT true of allosterically
regulated enzymes?
- Their activity can be modulated by effector molecules.
- They demonstrate cooperativity.
- Their activity can be modulated by substrate concentration.
- They follow Michaelis-Menten kinetics.
- Plots of their rate of product formation versus substrate
concentration are sigmoidal in shape.
CORRECT ANSWER : D. They follow Michaelis-Menten
kinetics.