Discussion 13: Problem Solving Final
MCB 150
Problem Solving IV
Final Exam Material
1. Compare and contrast the elements of negative and positive regulation in
the E. coli lac operon, including a description of the molecules involved.
2. Why don’t host RNA polymerases immediately start copying the genomes
of the RNA viruses described in class?
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Discussion 13: Problem Solving Final
MCB 150
3. SpeI (pronounced "S-P-E-One") is an enzyme that recognizes the 5'-3'
sequence ACTAGT and cuts between the first adenine and the cytosine.
XbaI ("ex-bah-one") recognizes the 5'-3' sequence TCTAGA and cuts
between the first thymine and the cytosine. If one ds-DNA sample is
digested with SpeI, and a second ds-DNA sample is digested with XbaI
and the fragments mixed together with DNA ligase, can any recombinant
molecules be generated?
Follow-up question: Will the recombinant fragments in the previous question be
recognized and cut by SpeI, XbaI, both, or neither?
4. You decided to study how organelle transport occurs in cells. Your
approach was first, to assemble microtubule tracks on a glass slide (for
microscopy); second, to add purified liposomes and ATP; third, analyze
through a light microscope the movement of liposomes. To your
disappointment no movement of liposomes was observed. What
hypothesis would most likely explain your experimental observation?
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Discussion 13: Problem Solving Final
MCB 150
5. You repeated the same experiment as that in the previous question, but
instead of liposomes, you added transport vesicles, which were isolated
from mammalian cells. This time, a rapid movement of the vesicles was
observed. What was your conclusion(s)?
6. You would like to study the molecular mechanisms of flagella movement.
You decided therefore to isolate the flagellum of a sperm, and observe its
movement in a physiological buffer. You make the interesting observation
that while the flagellum was bending well initially, it rapidly stopped any
movement. What was your hypothesis to explain this data?
7. Which experiment would you perform to test your hypothesis from the
previous question? Indicate the expected result.
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