Exam 17: Control of Gene Expression in Bacteria

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.?

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

A distinct part of a protein that often has a distinct function is a

Imagine that you discover a bacterial operon involved in the synthesis of vitamin B₁₂.This operon is regulated by a repressor protein that binds to an operator sequence.Vitamin B₁₂ is the allosteric effector of the repressor-the molecule that binds to the repressor to affect its activity.Predict how vitamin B₁₂ will influence repressor activity.

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

E)coli and many other bacteria of the human gut need to have fine-tuned regulation of gene expression in order to

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

Introducing the recombinant lac operon/mouse tyrosinase DNA into mice is only half of the equation for regulating tyrosinase.In addition to lac operon/mouse tyrosinase DNA,what other gene must be added to mice to regulate tyrosinase expression?

The particular amino acid sequence in the helix-turn-helix domain of a regulatory protein

Negative control occurs when

The product of the lacI gene is

In negative control of transcription,a gene is activated when

Use the following information when answering the corresponding question(s). 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?

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

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

CAP is said to be responsible for positive regulation of the lac operon because

What is an inducer?

Catabolite activator protein (CAP)activity is controlled by cAMP at the ________ level.