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BIO 340 Exam 4 Questions with Correct Answers Graded A+
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BIO 340 Exam 4Questions with
Correct Answers
Graded A+
Denning Muriithi [Date] [Course title]
, BIO 340 Exam 4
1. In negative control, what molecule would you expect to find bound to
the operator if there is no transcription? Correct Ans: repressor
2. You want to design a repressor protein mutant. Which protein domain is
the best target for preventing binding of the corepressor? Correct Ans:
allosteric domain
3. The presence of which combination of molecules could prevent
transcrip- tion of a repressible operon? Correct Ans: repressor +
corepressor
4. What are the two active sites or "domains" on a repressor protein?
Correct Ans: DNA binding site
Allosteric site
5. If a corepressor is inhibited, what effect would you expect to see on
tran- scription in a repressible operon? Correct Ans: Transcription will
occur.
6. Most of the regulation of gene expression in bacteria occurs at the
. Correct Ans: level of transcription
7. Changing conformation at the active site as a result of binding a
substance at a different site is known as . Correct Ans: allostery
8. In the lac operon, what acts as the inducer? Correct Ans: allolactose
9. The enzyme ²galactosidase catalyzes what reaction? Correct Ans:
lactose ’ galactose + glucose
10.A bacterium is unable to transport lactose into the cell to be broken
down. Which gene is likely mutated in this bacterium? Correct Ans: lacY
11.In the presence of glucose, where is the lac repressor bound? Correct
Ans: lacO
12.Which molecule functions as the corepressor in the trp operon?
Correct Ans: trypto- phan
13.In the absence of tryptophan, Correct Ans: the inactive repressor
cannot bind trpO, so operon gene transcription occurs.
14.Which proteins facilitate RNA polymerase binding at promoters to
increase levels of transcription? Correct Ans: activator proteins
15.Which of the following mutations could lead to constitutive expression
of the genes of the lac operon? Correct Ans: A mutation in the operator
sequence
(Such a mutation could prevent binding of the repressor, allowing
expression under all conditions.)
16.Which of the following best describes the biological role of the lac
, BIO 340 Exam 4
oper- on? Correct Ans: It ensures that a cell dedicates resources to the
production of enzymes involved in lactose metabolism only when
lactose is available in the environment.
(The cell expends energy to produce the proteins necessary for lactose
metabolism only when lactose is present.)
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