Exam 18: Control of Gene Expression in Bacteria

Under what condition is the AraC protein an activator? When AraC is bound to

Which of the following environments would most likely lead to the transcription of the lactose operon?

Which phenotype would be observed in an E. coli cell with the lacY- genotype?

To date, several lactose metabolism mutants have been found in Escherichia coli. One of these mutants has a phenotype in which the cell cannot accumulate lactose because no lactose permease protein is present. What genotype would be associated with this mutation?

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

A group of genes that are regulated together and transcribed into a single mRNA is

In the first step of their experiments, Jacob and Monod treated E. coli cells with UV light or X- rays in order to

What is the common theme of global gene regulation?

Use the following information when answering the corresponding questions). The lac operon is used in countless ways for genetics research and biotechnology. One important use of the lac operon is to regulate the expression of cloned genes. In this application, some regulatory elements of the operon are fused to the cloned gene that is to be regulated. One application of such technology was reported by Cronin et al., The lac operator- repressor system is functional in the mouse, Genes and Development 15 2001):1506-17. These investigators fused a portion of the lac operon to the mouse tyrosinase gene, a gene required for pigment production. This recombinant DNA, composed of E. coli lac operon sequences and the mouse tyrosinase gene, was introduced into albino mice using techniques described in Chapter 19. Using the lac operon regulatory sequences, the investigators were able to regulate tyrosinase gene expression. In fact, they were able to convert albino white) mice into brown mice. The following questions ask you to use your knowledge of the lac operon to deduce how Cronin et al. were able to regulate tyrosinase gene expression in mice. -The tyrosinase gene used by Cronin et al. contained the protein- coding sequence and the normal mouse regulatory sequences. These regulatory sequences provide positive control of tyrosinase transcription. If nothing else is done to this DNA and it is introduced into a mouse, tyrosinase will always be expressed. Because the goal was to regulate expression of tyrosinase, what portion of the lac operon do you think was added to this mouse gene?

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

Controlling the production of a pigment is interesting, but in itself seems more a stunt than a valuable research endeavor. What is the broader significance of the results of Cronin et al.?

Imagine that you've set up a genetic screen to identify E. coli mutants that cannot metabolize the amino acid tryptophan. 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

The situation in which an active regulatory protein "turns on" gene expression is an example of which of the following?

What proteins) is/are responsible for the dual positive and negative control of the ara operon?

Recall that cyclin- dependent kinases are activated when they bind to a cyclin protein. This form of regulation is

In negative control of transcription, a gene is activated when

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?

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