All cells have the same genome. What genes they have regulated on == cell function.

Gene Expression Regulation

Cells use gene regulation:

• to conserve energy.
• to allow cell specialization.
• to respond to environmental changes.

Chromatin Structure

Wrapped dna is not accessible. Either open or closed.

Heterochromatin

Closed chromatin

Not accessible dna.

Euchromatin

Open chromatin.

DNA is accessible.

Transcriptional Control

Making RNA & Epigenetics

Post-Transcriptional Control

Processing mRNA

Translational Control

Making proteins

Post-Translational Control

Modifying proteins

Differential Gene Express

Allows cell specialization.

Epigenetics

A process that produces huge differences in phenotypes from environmental factors that modifies genes w/o changing the genome sequence.

Transcriptional Control

Controls if and how much mRNA is made. Controls if chromatin is open or closed.

Translation Control

Does the protein get made?

Post-Translational Control

How does the protein get folded/processed?

Gene Transcription Factor Proteins

Proteins that influence whether expression starts or not. Combinatorial control - most genes require multiple transcription factors.

Basal Transcription Factors

Generic, genes are always transcribed at moderate rates.

Activators Enhancers

Speeds up transcription.

Positive gene expression.

Repressors Silencers

Slows down transcription.

Negative gene expression.

Epigenetic Inheritance

Epigenetic changes can be inherited.

Dutch hunger winter

2 Ways Epigenetics works

Acetyl groups (tags) placed on histone proteins tell the chromatin to open. Methyl groups (tags) placed on DNA tells the chromatin to close.

Modifications (tags) that influences chromatin structure.

• Tags are placed on DNA/histones
• Epigenetics influences chromatin structure

DNA Methylation Methyl Groups (tags)

Influences open vs closed DNA without changing DNA sequences (the A/G/C/Ts)

• When DNA is supercoiled and not accessible for transcription, it exists as condensed heterochromatin

• When the DNA is loosely packed and therefore accessible to the transcription machinery, it exists as euchromatin

Histone Acetylation Acetyl Groups (tags)

Acetyl groups are attached to an amino acid in a histone tail

• Reduces the positive charge of the histone

• This appears to open up the chromatin structure, thereby promoting the initiation of transcription

When gene expression needs to be turned off, histone deacetylases (HDACs)remove acetyl groups and DNA becomes tightly wound and inaccessible again.

Post-Transcriptional Regulation

Regulation Doesn't Stop at Transcription

• Once mRNA is made, can still be regulated
• We'll briefly touch on one major mechanism that we have talked about already – splicing!
• This adds flexibility and speed to gene regulation

Antibodies - membrane bound version detects germs - stays on the cel surface, can be secreted (released from the cell) to fight germs. It's the same gene, but differs in whether the last exon is included or not.

Efficient, so one gene can do 2 jobs quickly.

Alternative Splicing

One gene can make multiple proteins.

Can't change order, can't duplicate exons.

Different exon combinations in different cell types.

Increases protein diversity without increasing genome size.

Gene can produce many diff. proteins (can remove exons, through the removing of exons).

Gene Regulation

Splicing can be regulated

Controls which proteins are made