Epigenetics Flashcards
What is meant by epigenetics?
> Provides explanations as to how environmental influences e.g. stress, diet, toxins can subtly alter the genetic inheritance of an organisms offspring
What proteins wrap around DNA?
> Histones
What are both the DNA and histones covered in?
> Chemical tags
The chemical tags wrapped around the DNA and histones form a second layer, known as..?
> The epigenome
What does the epigenome determine?
> The shape of the DNA-histone complex
> It keeps genes that are inactive in a tightly packed arrangement and therefore ensures they cannot be read (keeps them switched off) -> this is known as epigenetic silencing
> It unwraps active genes so that the DNA is exposed and can easily be transcribed (switches them on)
The DNA code is fixed. The epigenome however is..
> Flexible, because it’s chemical tags respond to environmental changes
> Factors like diet & stress can cause the chemical tags to adjust the wrapping and unwrapping of the DNA and so switch genes on and off
The DNA-histone complex (chromatin)
> Where the association of histones with DNA is weak, the DNA-histones complex is less condensed, so the DNA is accessible by transcription factors
(Gene is switched on)
> Where the association of histones with DNA is strong, the DNA-histones complex is more condensed, so the DNA is not accessible by transcription factors
(Gene is switched off)
Decreased acetylation of associated histones
> Acetylation = An Acetyl group is transferred to a molecule
> Decreased acetylation increases the positive charges on histones and therefore increased their attraction to the phosphate groups of DNA
The association between DNA and histones is stronger and the DNA is not accessible to transcription factors
Increased methylation of DNA
> Methylation is the addition of a methyl group to a molecule ( added to the cytosine bases of DNA )
> Inhibits the transcription of genes in two ways:
• Preventing the binding of transcriptional factors to the DNA
• Attracting proteins that condense the DNA-histone complex, making the DNA inaccessible to transcription factors
