Question 1

Mutagenic studies of the promoter region of the fi -globin gene indicate that some areas are more likely than mutations in other areas to affect transcription rates. When
mutations occur in consensus sequences (modular elements such as GC box, CAAT box, TATA box), does transcription increase or decrease?

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Question 2

What is the location of an enhancer in relation to the gene it affects?

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Question 3

What experimental results would indicate that the mutation lacIs is dominant to lacI+?

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Question 4

The catabolite repression system in E. coli essentially represses the lac operon when glucose is present. What evolutionary advantage would favor evolution of such a
system?

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Question 5

Within the control region of the trp operon is a section of DNA that is sensitive to levels of tryptophan in the system. What is the name of this region?

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Question 6

What symbols are used to describe constitutive mutations at specific regions of the lac
regulatory system?

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Question 7

Regarding regulation of the trp operon, what might one appropriately call the amino acid tryptophan?

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Question 8

Regarding the trp operon, trpR - maps to a considerable distance from the structural genes. The mutation either inhibits the interaction with tryptophan or inhibits
repressor formation entirely. In the presence of tryptophan in the medium, would you expect the trp operon to be transcriptionally active? Explain.

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Question 9

In what way is chromosomal organization within the nucleus of an interphase cell thought to be related to gene activity?

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Question 10

State whether the following statement is true or false; then give your reasoning: The terminating "hairpin" loop occurs in the trp operon when sufficient tryptophan is
present.

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the hairpin loop terminates transcription.

Question 11

The cAMP -CAP complex and RNA polymerase bind more efficiently to the lac operon together than either does alone. What term is applied to this increased efficiency of
binding?

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Question 12

Describe how nucleosomes may influence gene transcription.

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Question 13

Describe three characteristics of enhancers.

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Question 14

Monod discovered that if tryptophan is present in relatively high quantities in the
growth medium, the enzymes necessary for its synthesis are repressed. How does this occur?

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Question 15

Name at least three different levels of regulation in eukaryotes.

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Question 16

Mutations in the lacI and lacO genes of the lac regulatory system in E. coli often lead to full transcription of the three structural genes, even when no lactose is available to the organism. Such mutations would be called _.

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Question 17

Describe the function and general nature of promoters in eukaryotes.

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Question 18

Describe the positive control exerted by the catabolite activating protein (CAP). Include a description of catabolite repression.

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Question 19

What is an allosteric molecule?

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Question 20

Approximately 5 percent of the cytosine residues are methylated in the genome of any given eukaryote. In what way is DNA methylation related to genetic regulation?

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Quiz 15: Regulation of Gene Expression