gene 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

What is gene expression?

Gene expression is the process by which information from a gene is used to make a functional product, such as a protein or RNA molecule.

What is gene regulation?

Gene regulation is the control of when, where, and how much a gene is expressed, determining whether a gene is turned on or off in a cell.

What are three things gene regulation allows cells to do?

1. Respond to changes in the environment. 2. Specialize into different cell types (cell differentiation). 3. Conserve energy by only producing proteins when needed.

Why do skin cells and nerve cells differ despite having the same DNA?

They differ because gene regulation causes different genes to be expressed in each cell type.

Which cell type expresses the gene that codes for the protein myosin?

Muscle cells express the gene that codes for myosin.

Are housekeeping genes always expressed, never expressed, or sometimes expressed?

Housekeeping genes are always expressed because their products are essential for basic cell functioning.

What triggers gene expression?

Gene expression is triggered by internal signals (like proteins or hormones) or external signals (like changes in temperature, light, or nutrients).

Why are most eukaryotic genes 'off' by default?

Most eukaryotic genes are off by default because producing proteins requires energy, so cells only turn genes on when needed.

What happens if the promoter of a gene is mutated?

If the promoter is mutated, RNA polymerase may not bind properly, resulting in reduced, increased, or completely blocked expression of the gene.

What are the three main stages of transcription?

The three main stages of transcription are initiation, elongation, and termination.

What is a transcription factor?

A transcription factor is a protein that regulates gene expression by binding to specific DNA sequences, influencing the transcription of genes.

What do regulating proteins recognize along sequences of DNA/RNA?

Specific sequences or motifs.

What is splicing?

The process of removing introns and joining exons in pre-mRNA.

Why is splicing important?

It allows for the production of multiple protein products from a single gene.

What is alternative splicing?

A process that results in a single gene making a variety of protein products.

How does alternative splicing increase cellular efficiency?

It reduces the amount of genetic material required to code for many proteins.

What are the three main stages of translation?

Initiation, elongation, and termination.

What can DNA mutations result in?

Altered gene expression patterns.

What happens when mistakes occur in DNA nucleotide sequences?

They can be transcribed and translated, resulting in mutated or faulty protein products.

How can mutations in gene regulating molecules affect gene expression?

They can disrupt normal gene expression.

What is a potential consequence of gene regulation breakdown due to mutations?

Diseases such as cancer.

What characterizes cancer at the cellular level?

Continual cell division and growth.

What is the location of transcription in prokaryotes?

Cytoplasm

What is the location of transcription in eukaryotes?

Nucleus

How many RNA polymerases are present in prokaryotic transcription?

One

How many RNA polymerases are present in eukaryotic transcription?

Three

Do prokaryotes have a nucleus?

No

Do eukaryotes have a nucleus?

Yes

Is mRNA processing present in prokaryotic transcription?

No

Is mRNA processing present in eukaryotic transcription?

Yes

What types of mRNA processing occur in eukaryotes?

5' cap, poly-A tail, splicing (removing introns)

What is the speed of transcription in prokaryotes?

Faster

What is the speed of transcription in eukaryotes?

Slower

Can transcription and translation occur simultaneously in prokaryotes?

Yes

Can transcription and translation occur simultaneously in eukaryotes?

No

In which organisms would you find prokaryotic transcription?

Bacteria

In which organisms would you find eukaryotic transcription?

Humans, plants, animals

What is the ribosome size in prokaryotic translation?

70s

What is the ribosome size in eukaryotic translation?

80s

What is the initiator tRNA in prokaryotic translation?

fMet

What is the initiator tRNA in eukaryotic translation?

Met

What is the start codon in both prokaryotic and eukaryotic translation?

AUG

Is prokaryotic translation coupled with transcription?

Yes

Is eukaryotic translation coupled with transcription?

No

How does mRNA processing increase protein diversity in eukaryotic cells?

It allows different combinations of exons to be joined together through alternative splicing.

Why can transcription and translation occur at the same time in prokaryotes?

Because prokaryotes do not have a nucleus, both processes happen in the cytoplasm.

What is one similarity between prokaryotic and eukaryotic transcription?

Both use RNA polymerase to make mRNA from DNA.

What is one difference between prokaryotic and eukaryotic transcription?

Eukaryotic transcription requires mRNA processing, while prokaryotic transcription does not.

Is an organism with mRNA containing introns more likely prokaryotic or eukaryotic?

Eukaryotic, because prokaryotes do not have introns.