S$7$A Problem Solving Session $7($Week $8)$

$1.$ Using any available course resources define the purpose of the following in terms of prokaryote gene regulation.

Negative Control: Positive Control: Bacterial Chromosome: Plasmid:

Operon:

Operator:

Promoter:

Repressor:

Activator:

Inducer:

Catabolite Activator Protein: Cis Element:

Trans Element:

$2.$ Describe the DNA model below to your LA or neighbor using the terms defined above. Then, draw out where the components $($lac repressor, inducer, activator, and RNA polymerase$)$ would be located if there were no lactose and low glucose present.

For the following conditions, indicate if there will be high, low, or no expression of the lacZ, LacY, and LacA genes. In the space provided below the condition write your reasoning and then explain it to your LA or neighbor.

$3.$ No lactose and low glucose present.

Reasoning:

$4.$ High lactose and low glucose.

Reasoning:

$5.$ No lactose and high glucose.

Reasoning:

$6.$ High lactose and high glucose.

Reasoning:

$7.$ High lactose, low glucose, and a loss$-$of$-$function mutation in Plac.

Reasoning:

$8.$ No lactose, low glucose present, and a loss$-$of$-$function mutation in PI$..$

Reasoning:

$9.$ Imagine a bacterium that contains both a chromosomal copy of the lac operon and a plasmid copy of the lac operon represented below by I O Z$.$ Flip a coin to determine the mutation status of each element $($I O Z$).$ Heads is Mutated $(-$ or c$)$; tails is Wild Type $(+).$ Then determine the level of LacZ expression.

Chromosome:I O Z Plasmid:I O Z