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USABO Open Exam 2006.
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USABO Open Exam 2006Insulin 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. - correct 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. - correct 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 - correct 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 - correct 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 - correct 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 - correct 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. - correct 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 - correct 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
D. 4, 2, 1, 3, 5
E. 5, 3, 4, 1, 2 - correct answer-C. 3, 5, 1, 4, 2
When bacterial cells multiply maximally during the logarithmic phase, the total number of
cells (b) after some time interval (t) is equal to the original number of cells (B) multiplied by
2n , where n is the number of generations formed during the time interval: n = t/g and b =
(B)(2n ). The generation time (g) for type A cells is 28 minutes (assume no cell death).
Estimate the LEAST amount of time required for a population of type A cells to increase by
300 percent.
A. approximately 42 minutes
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