L17: Environmental Effects and Epigenetics Flashcards
Why is epigenetics important clinically?
Epigentic mechanisms are ‘drugable’
What is epigenetics?
The study of how genes can be turned on and off by mechanisms other than gene sequence, using enzymes
Which genes are turned on in all cells?
‘Housekeeping genes’ e.g. histones, RNA polymerase, tubulin, pyruvate kinase
What is a gene?
1.
2.
- Structural information coding for a protein
2. Regulatory sequences giving instructions for expression
5’ regulatory sequence controls what?
What is this region called?
controls transcription initiation
promotor
What does a TATA box do?
marks the beginning of a gene
What do general transcription factors do?
Recognise true gene promoter
Recruit RNA polymerase II to gene
Initiates transcription
What are the two types of transcription?
Basal level of transcription
Activated transcription
Rates of transcription are controlled by
1.
2.
- enhancers (DNA sequences up and downstream of gene)
2. gene-specific transcription factors
………. ……….. highlights the gene. Transcription factors act as a …………. to initiate transcription
Basal machinery
committee
What is chromatin?
packaged DNA
What is a nucleosome?
DNA packaged around 8 histones, assembles about 200bp of DNA
What are the 2 examples of epigenetic?
histone modification
X-inactivation
How do we know that histone tails are important in epigenetic?
They are identical in yeast and man, they have evolutionarily preserved
Why are histone tails important?
They act as chemcical tags, they can be modified (phosphorylation, glycosylation etc). Every amino acid is performing a role, structure not important as waving about
Involved in turning genes on or off, act as a second layer of regulatory information
Nucelosome modifications:
- Involved in …..
- Respond to ….
- Involved in turning genes on or off
2. Respond to changes in environment inside and outside of cell
Why is X-inactivation required?
Females have two X’s, males have one X and one Y
In females one of the 2 X’s are inactivated early in development.
Dosage compensation equalises gene expression levels.
How does X-inactivation manifest?
The inactive X chromosome becomes a densely staining Barr body
X inactivation is ………….
It occurs in the …….. cell mass of the blastocyst
Inactive state is ………… …. to succeeding cell generations
X-inactivation is an example of a heritable ………….. ……..
random
inner
passed on
epigenetic state
