Use the Following Information When Answering the Corresponding Questions)

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?

A) the lacI gene
B) the lacZ gene
C) CAP
D) the lacY gene
E) the lac operator