USABO OPEN EXAM QUESTIONS AND ANSWERS GRADED A+ 2025/2026

USABO OPEN EXAM QUESTIONS AND
ANSWERS GRADED A+ 2025/2026




What enzyme does HIV use to convert RNA to DNA?


A. DNA gyrase
B. RNA polymerase
C. Reverse transcriptase

D. DNA helicase - ANS C. Reverse transcriptase


The promoter region of a prokaryotic gene is located ______ to the gene and is the binding site
for ______.


A. 3'...DNA polymerase
B. 3'...RNA polymerase
C. 5'...DNA polymerase

D. 5'...RNA polymerase - ANS D. 5'...RNA polymerase


Which of the following is TRUE of prokaryotes?
I. Simultaneous transcription and translation
II. Presence of intron sequences
III. Circular DNA




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, A. I and II only
B. I and III only
C. II and III only

D. I, II, and III - ANS B. I and III only


Integral transmembrane proteins are proteins imbedded in the cell membrane. Which of the
following amino acids would you MOST expect to find in the transmembrane region of such
proteins?


A. Lysine
B. Serine
C. Tryptophan

D. Arginine - ANS C. Tryptophan


When the base composition of DNA from bacterium Mycobacterium tuberculosis was
determined, 18% of the bases were found to be adenine. What is the G + C content in M.
tuberculosis?


A. 18%
B. 32%
C. 36%

D. 64% - ANS D. 64%


The frequency of individuals affected with an autosomally recessive inherited disorder is 1 in 4.
Assuming that the population affected by this disease is in Hardy-Weinberg equilibrium, what is
the proportion of carrier individuals in this population?


A. 12.5%
B. 25%
C. 50%


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