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Exam 18: Control of Gene Expression in Bacteria

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Question 1

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Bacterial and eukaryotic cells primarily control gene expression at the level of transcription. If instead cells exerted control of gene expression primarily at the post-translational level, what would be different?

A) The ability to rapidly respond to environmental change would be reduced.
B) Cells would expend significantly more energy.
C) Genes would no longer be transcribed.
D) Translation of mRNA into protein would not occur.

E) All of the above
F) B) and C)

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Question 2

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If you wanted to prevent a regulatory protein from changing gene expression, you would have to prevent physical contact between the protein and ________.

A) ribosomes
B) DNA
C) ribozymes
D) mRNA

E) B) and C)
F) C) and D)

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Question 3

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Which of the following is a protein produced by a regulatory gene?

Although the expression of most genes is tightly regulated, some genes are expressed at roughly constant rates. Which of the following genes would you predict to be constitutively (constantly) expressed?

Which of the following levels of gene expression allows the most rapid response to environmental change?

Use this information to answer the question(s) below. -If she moves the promoter for the lac operon to the region between the beta galactosidase (lacZ) gene and the permease (lacY) gene, which of the following would be likely?

Altering patterns of gene expression in prokaryotes would most likely serve an organism's survival by ________.

An E. coli cell without a functional lacI gene is expected to ________.

Most repressor proteins are allosteric. Which of the following binds with the repressor to alter its conformation?

Under what condition is the AraC protein an activator?

One interesting and surprising finding regarding the regulation of the ara operon is that it is under both positive and negative control. What protein is responsible for the dual action of this operon?

According to the lac operon model proposed by Jacob and Monod, what is predicted to occur if the operator is removed from the operon?

The product of the lacI gene functions most like a car's ________.

Jacob and Monod were intellectually primed to draw the conclusions they did concerning regulation of the lac operon. In part, this was due to their fascination with mechanisms of enzyme regulation. They knew that the activity of some enzymes is regulated when their reaction product binds to the enzyme, changing its shape and, therefore, its activity. This knowledge allowed them to easily make the intellectual leap to propose ________.

There is a mutation in the repressor that results in a molecule known as a super-repressor because it represses the lac operon permanently. Which of these would characterize such a mutant?

The greatest expression of the lac operon occurs when lactose levels are ________.

Suppose several genes are grouped together in a bacterial genome and the group results in a single enzyme. If one of these genes is mutated and the enzyme is no longer active, this gene must be part of ________.

The arabinose operon (ara) provides a particularly interesting example of ________ in that when arabinose is present in the environment, the operon is transcribed.

In negative control, a gene is switched off when ________.

Imagine that you have set up a genetic screen to identify E. coli mutants that cannot metabolize the amino acid tryptophan for energy. Beginning with a master plate containing many colonies, you prepare replica plates on medium with glucose or tryptophan as the only energy source. You would look for colonies that ________.