USABO Open Exam Questions and
Answers
Insulin injected by diabetics to control blood sugar levels is derived from bacteria whose
DNA has been modified by the addition of the human gene for insulin, which is then
produced by the prokaryotes. This is an example of:
A. acid therapy.
B. cloning.
C. genetic engineering.
D. gene therapy.
E. pluripotency. - Answer -C. genetic engineering.
Isolated RNA molecules are generally less stable than DNA at physiological pH
because:
A. RNA has ribose.
B. RNU is always linear.
C. RNA has U instead of T.
D. RNA is usually single stranded.
E. there are many more RNAse enzymes. - Answer -A. RNA has ribose.
Which of the following molecules is able to cross the lipid bilayer?
A. antibodies
B. ATP
C. insulin
D. Na+
E. steroid hormones - Answer -E. steroid hormones
If the rate constant of a first order reaction that converts substrate S into product P is
0.693 min -1 then what is the half life of the reaction?
A. 0.010 min
B. 0.346 min
C. 0.693 min
D. 1.000 min
E. 1.440 min - Answer -D. 1.000 min
, The local swimming pool is contaminated with an organism that is causing "swimmers
itch." You think you have identified cyanobacteria in your sample. Which features would
you expect this organism to LACK?
A. chlorophyll
B. cell membrane
C. differentiated cell types such as spores, vegetative cells, and heterocysts
D. nucleoid region
E. nucleolus - Answer -E. nucleolus
Suppose radioactive thymine was added to an actively dividing culture of E.coli bacteria.
What would happen if a cell replicated once in the presence of this radioactive base?
A. one of the daughter cells, but not the other, would have radioactive DNA
B. neither of the two daughter cells would be radioactive
C. all four bases of the DNA would be radioactive
D. radioactive thymine would pair with nonradioactive guanine
E. DNA in both daughter cells would be radioactive - Answer -E. DNA in both daughter
cells would be radioactive
If radioactive sulfur ( 35 S) is used in the culture medium of bacteria that harbor
bacteriophage viruses, it will later appear in:
A. bacterial RNA.
B. bacterial cell walls.
C. viral DNA.
D. viral RNA.
E. viral coats. - Answer -E. viral coats.
Which of the following would probably be LEAST DAMAGED by a lipid-dissolving
enzyme (lipase)?
A. endoplasmic reticulum
B. mitochondria
C. ribosomes
D. nuclei
E. plasma membrane - Answer -C. ribosomes
Five events occur in a cell constituting a cause-and-effect sequence: 1. an enzyme is
manufactured at the ribosomes 2. cellulose is deposited in a cell wall 3. a molecule of
RNA is transcribed 4. a carbohydrate polymer is synthesized 5. a nucleic acid migrates
from nucleus to ribosome The order in which these events occur is:
A. 1, 3, 5, 4, 2
B. 2, 1, 4, 5, 3
C. 3, 5, 1, 4, 2
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