Gene Expression and Regulation: Key Concepts for Biology Students

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.