Prokaryotic Transcription

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Transcription

The process by which RNA is synthesized from a DNA template.

What is a promoter?

A DNA sequence that signals where RNA polymerase should bind to start transcription.

What is the transcription start site (TSS)?

The first DNA nucleotide that is transcribed into RNA.

What is the RNA polymerase holoenzyme?

A complex of RNA polymerase and sigma factor, necessary for promoter recognition.

What role does the sigma factor play?

It helps RNA polymerase recognize and bind to specific promoters.

What does polycistronic mRNA mean?

A single mRNA strand encodes multiple proteins, typically from an operon.

What is an operon?

A group of genes regulated together and transcribed into a single mRNA molecule.

Give an example of a prokaryotic operon.

The lac operon, which includes LacZ, LacY, and LacA.

What do transcription factors do?

They help or hinder the recruitment of RNA polymerase to the promoter.

What is a co-activator?

A protein that enhances transcription by helping transcription factors recruit RNA polymerase.

What is a co-repressor?

A protein that assists repressors in inhibiting transcription.

How does a repressor block transcription?

It binds to the operator region, preventing RNA polymerase from initiating transcription.

How does ligand binding affect transcriptional repressors?

Ligands can activate or deactivate repressors, affecting their DNA-binding ability.

What does LacZ encode?

β-galactosidase, which breaks down lactose into glucose and galactose.

What enables the lac operon to turn on?

Removal of the repressor and binding of the activator to the promoter region.

What is a consensus sequence?

A sequence of DNA with the most common bases found at specific positions (e.g., -10 and -35 regions upstream of TSS).

Why are prokaryotes useful model organisms?

They have fast replication, simple gene structure, and straightforward regulation.

What makes prokaryotic gene expression simpler than eukaryotic?

Fewer regulatory elements and predominance of polycistronic mRNAs.