Epigenetic control of development Flashcards
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Lecture 1
- Epigenetics
- What does epigenetics mean
- Epigenetic modifications
- DNA methylation
- Histone modifications
- Non-coding RNAs
- Early Development
- MZT
Lecture 2
- Development & epigenetics
- TE/ICM differentiation
- establishment of Tissue specific gene expression
- Effect of early life environment
- Maternal environment
- Paternal effects
What type of control do genes have in development?
They have temporal control

What type of tissue specific control do genes have?

Even though cells have the same DNA, what makes them different?
- Cells all have the same DNA
- It’s in the mRNA
- Make sure right genes are switched on in the right cells
What does epigenetic gene regulation ensure?
That genes are expressed in the right place at the right time

What is the definition of epigenetics?
Definition: Processes that induced long term stable changes in gene activity without a change in gene sequence
Why does a cloned cat show the importance of epigenetics?
A cloned cat shows the importance of epigenetics: although same DNA they are epigenetically distinct. Hence why carbon copy of animals shows physical differences
(look up photo of rainbow and Carbon copy)
What are the major epigenetic processes?
- DNA methylation
- Histone modification
- non-codign RNAs

Tell me about where DNA methylation occurs?
- Cytosine is methylated to 5-methyl cytosine
- 90% of methylated cytosine is found as a dinucleotide CpG

How does DNA methylation affect gene transcription?
- Methylation prevents the RNA polymerase binding and therefore transcription of gene occurring

What are the enzymes involved in DNA methylation and what is the role of each?
DNA methyl transferases (DNMTs)
- DNMT1: maintenance DNMT (copies marks from old strand onto the newly synthesised ones)
- DNMT3a and 3b: de novo DNMTs (establishes new methylation marks in the first place)
What are the DNA demethylase enzymes?
TET enzymes (ten-eleven translocation)
What do the TET enzymes do?
DNA demethylases: TET enzymes

Tet converts 5- methyl Cytosine (5mC) to 5-hydroxymethylcytosine (5hmC)
What does the state of histone govern?
The accessibility of DNA to RNA pol

What is chromatin a combination of?
Chromatin= DNA + histones
Whats a nucleosome and what is its structure?
- They are the basic unit of chromatin
- Have 4 different histone subunits: 2x H2a, 2xH2b, 2xH3 and 2x H4
- Histones are positively charged in order to interact with the negatively charged DNA to create a tight binding site

What are nucleosome further packaged to form?
Nucleosomes are further packaged to form a 20nm fibre or solenoid

A solenoid

What is the type of binding in a solenoid and what does this determine?
The binding may be loose or tight (depends on state of histones)

What 2 domains does the histone have?
- Globular domain (C- terminal)
- Amino tail domain (N-terminal, lots of lysine’s)

The histone tails are subject to modification
What does the position and type of modification of the tail determine?
Whether binding is loose or tight DNA is in an open or condensed form Gene is active or repressed
What is histone acetylation associated with?
Gene activity
What happens in histone acetylation to promote increased gene activity?
- The acetyl groups are present on the histone ‘tails’
- The histones are no longer tightly packed
- The promoter and target gene are now accessible to transcription factors and RNA polymerase
- Acetylation of the lysine’s in the tail neutralises their charge (lysine’s are positively charged)
- This reduces the affinity of the tail for the DNA
- Opens up DNA allows RNA pol to bind and the gene to be active

What enzyme is involved in lysine acetylation?
HAT











































