Exam 2 deck 4

Question 1

Gene expression

Answer 1

when the molecule the gene codes for has been produced

Question 2

Constitutive genes

Answer 2

genes that are always expressed at a fixed rate

-usually for vital products

Question 3

Repressible genes

Answer 3

genes that are ON by default, but can be turned off by repressors

Question 4

Inducible genes

Answer 4

genes that are OFF by default, but can be turned on by inducers

Question 5

Operon

Answer 5

set of operator and promotor sites as well as the genes that they control

Question 6

Promoter

Answer 6

site at which RNA Polymerase begins the transcription of the structural genes

Question 7

Operator

Answer 7

Segment of DNA that controls the transcription of the structural genes

Question 8

Explain how the lac operon works

Answer 8

Usually, the regulatory gene (lac I) produces a repressor mRNA which binds to the operator which stops transcription of structural genes. When allolactose is present, it binds to the repressor protein , enabling transcription to occur

Question 9

Explain how the trp operon works

Answer 9

Regulatory gene, I, makes inactive repressor proteins. When tryptophan is present, it becomes a corepressor and both of them bind to the operator, stopping transcription

Question 10

Explain catabolic repression in the lac operon

Answer 10

Low glucose inactivates adenylate cyclase, so more cAMP is made. cAMP binds to CAP (a receptor protein) and they both bind to the promoter, making it easier for RNA polymerase to bind.
If glucose levels are high, no cAMP is made and so the lac operon is off