Gene Expression and Regulation

What is Gene Expression?

process by which a gene produces its product and the product carries out its function

What is Gene Regulation?

The regulation genes allows cells to better respond to stimuli and conserve energy/materials

How do Prokaryotic cells turn genes on and off?

By controlling transcription

In Prokaryotes, where is DNA found?

Found in the cytoplasm

True or False?

In prokaryotes transcription and translation happen at the same time.

True

In prokaryotes, when is gene expression regulated?

at the start of transcription

In Prokaryotes, what controls the start of transcription?

promoters and operators

What is a promoter?

a DNA segment that allows a gene to be transcribed; helps RNA polymerase find where the gene starts.

What is an operator?

a DNA segment that turns a gene "on" or "off"

How are prokaryotic genes arranged?

Arranged into an operon

What is an operon?

promoter, operator, and all genes for proteins needed to do a task

What is the Lac Operon?

contains 3 genes coding for enzymes used to breakdown lactose

What happens when lactose is absent?

The lac operon is switched off to prevent transcription and save the cell's resources.

How does a repressor work?

binds to the operator preventing RNA polymerase from transcribing the gene

What happens when lactose is present?

The lac operon is switched on to allow transcription.

When lactose is present, how does it effect the repressor and gene expression?

Lactose binds to the repressor protein, changing its shape, causing the protein to fall off the operator, RNA polymerase binds and transcribes the genes.

Where do eukaryotic cells regulate gene expression?

at many points

What happens at the start of transcription in eukaryotic cells?

regulatory DNA sequences are recognized by transcription factors that bind to the DNA strand and help RNA polymerase know where a gene starts.

Most eukaryotic genes have what kind of promoter?

A seven nucleotide promoter (TATAAAA) called the TATA box.

What are enhancers?

sequences that speed up transcription

What are silencers?

sequences that slow down transcription

How can eukaryotic DNA bring all the elements needed to start transcription together?

DNA bends to bring all the elements together

What happens before mRNA can leave the nucleus?

introns and cut out and exons are bound together

What are exons?

nucleotide segments coding for parts of the protein

What are Introns?

noncoding regions of DNA

how can genetic diversity be increased without increasing the size of the DNA strand?

removal of introns

Why is a cap added to mRNA?

so the ribosome knows where to bind and prevent the immediate breakdown of mRNA

Why is a tail added to mRNA?

to help the mRNA exit the nucleus

What is cell differentiation?

process by which unspecialized cells develop into specialized cells.

What is responsible for cell differentiation?

gene expression