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a. What does a comparison of lanes 1 and 4 tell you?

b. What do lanes 2 and 3 show, and why might this be important?

c. How is lane 5 different from the other lanes? What does this lane show?

NOTE: by "what does this show," I mean "what important biological information does this convey," not "what are the molecules in this lane and how are they visualized." I'm looking for interpretation.

2. (3 pts) The GAL1 promoter is tightly regulated. Genes under the control of this promoter are expressed at very low levels when cells are grown in glucose, and strongly induced in the presence of galactose.

a. Why was the YAR1 gene cloned backward after the GAL1 promoter as well as forward? What would be the effect of expressing an "antisense" mRNA at high levels? (You may want to consult your textbook to answer this question.)

b. What was the effect of overexpression of YAR1? Why might this be important?

c. What was the effect of overexpression of antisense YAR1 mRNA? What does this finding suggest?

3. (2 pts) Explain why the findings discussed in section d, page 37, had at least two possible interpretations: slow germination or slow mitotic growth rate. How were these two possible interpretations tested? What was the result? (Germination of a spore refers to its initial mitotic division after exposure to a rich growth medium.)

4. (2 pts) Look up the regulation of trasncription factor NFkappaB in your textbook. Briefly explain the role of IkappaB in regulation of NFkappaB, and how IkappaB is in turn regulated. What is the connection between this system and YAR1?

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