The Lac Operon quiz Flashcards

In the absence of lactose, the lac operon is off or inactive because the repressor protein lac I binds to the operator, blocking RNA polymerase and preventing transcription.

The genes in the lac operon are lac Z, lac Y, and lac A, and they are needed to metabolize lactose and break it down for energy.

Lac I binds to the operator and blocks RNA polymerase, preventing transcription of the lac operon genes.

When lactose is present, a derivative called allolactose binds to and inactivates the repressor protein lac I, allowing RNA polymerase to initiate transcription of the lac operon.

RNA polymerase binds to the promoter and initiates transcription of the lac operon genes.

In the presence of glucose, the lac operon is turned off because glucose is the preferred energy source, and cAMP levels are low, reducing the transcription rate of the lac operon.

There is an inverse relationship; high glucose levels result in low cAMP levels, and low glucose levels result in high cAMP levels.

High cAMP levels increase the rate of transcription of the lac operon when glucose is low or absent.

Glucose is the preferred energy source for most prokaryotes, even in the presence of lactose.

When both glucose and lactose are present, the lac operon is typically turned off because glucose is the preferred energy source.

The lac Z gene encodes β-galactosidase, an enzyme that breaks down lactose into glucose and galactose.

Allolactose binds to the lac repressor protein, inactivating it and preventing it from binding to the operator, thus allowing transcription.

The lac Y gene encodes permease, which facilitates the entry of lactose into the cell.

The lac A gene encodes transacetylase, which is involved in the metabolism of lactose.

Low glucose levels result in high cAMP levels, which increase the transcription rate of the lac operon.