Final Lac Operon

Front 1

Lac operon

Back 1

part of lactose catabolism, the breaking down of the lactose molecule into galactose and glucose

Front 2

β-Galactosidase,
galactosidase permease,
transacetylase

Back 2

enzymes coded for by the structural genes of the lac operon

Front 3

Induction of transcription:

Lactose, an inducer, act to induce the transcription of the structural genes of the lac operon.

Lactose binds to and inactivates the?

Back 3

Repressor gene.

In the lac operon, the repressor is ALWAYS ON. When lactose is present, it binds to the repressor protein, inactivating it.

Front 4

Lac repressor gene

Back 4

DNA that codes for repressor protein.
always turned on.
it is not regulated.

Front 5

The naked lac repressor is

Back 5

active. when lactose is present, lactose binds to it and inactivates it, permitting transcription of the operon.

Front 6

Inducible operon

Back 6

transcription is induced by the presence of an inducer

Front 7

lac operon default situation

Back 7

lactose absent, repressor active, operon off.

repressor is an allosteric protein. active in the absence of lactose, inactive when bound to lactose.

Front 8

Polycistronic mRNA

Back 8

lac operon produces polycistronic mRNA. Many enzymes, many polypeptides

Front 9

Type of control

Back 9

positve

Front 10

Transcription stimulated by

Back 10

Lac operon

Front 11

Associated w/ which type of metabolism?

Back 11

catabolism. breaking down of lactose into galactose and glucose

Front 12

Is "naked" repressor active in lac?

Back 12

Yes, active, naked repressor binds to operator. When lac binds to it, it changes its active conformation, thereby releasing itself from the operator permitting transcription.

Front 13

Polycistronic mRNA?

Back 13

yes

-Polycistronic mRNA is one that codes for several structural proteins (enzymes)
-associated w/ enzymes

Front 14

CAP (catabolite activator protein) involved?

Back 14

yes

Front 15

operon =

Back 15

operator + promoter + structural genes

Front 16

Effect of glucose on lac operon

Back 16

catabolite repression

when glucose is present, lac operon is off.

Front 17

CAP and cAMP?

Back 17

catabolite activator protein and cyclic AMP. cAMP binds to CAP to make it active. CAP binds to promoter and enhances promoter's affinity for RNA polymerase

Front 18

CAP, what type of control?

Back 18

Positive gene regulation: CAP encourages (positive) RNA polymerase to bind to the promoter; CAP does not block anything.

Front 19

When lactose is present and glucose is scarce, what happens?

Back 19

cAMP level is high and abundant lac mRNA synthesized

Front 20

When lactose is present and glucose is present, what happens?

Back 20

Little lac mRNA is synthesized, cAMP level is low.