Acetylation and methylation Flashcards
- Define what is meant by epigenetics?
Heritable changes in gene function; Without changes to the base sequence of DNA;
- What is the epigenome?
Chemical tags such as acetyl and methyl that determines the shape of the DNA-histone complex. This makes it easier or harder for the DNA to be transcribed.
- What causes changes in epigenetics?
Changes in the environment, such as diet or stress.
- What does acetylation affect?
Acetylation affects histones.
- What does methylation affect?
Methylation affects DNA.
- How does the DNA-histone complex affect transcription?
When the DNA is strongly condensed around histones it is harder for transcriptional factors and RNA polymerase to bind to DNA and begin transcription. When the DNA is loosely condensed around histones it is easier for transcriptional factors to bind to DNA and begin transcription
- What is acetylation of histones?
An acetyl group is transferred from acetylcoenzyme A, this decreases the positive charges on histones and decreases their attraction to the phosphate group of DNA. The association between DNA and histones is weaker, and therefore more accessible to transcription factors. This means that the gene is switched on.
- What is methylation of DNA?
The addition of a methyl group to the cytosine bases of DNA. This prevents the binding of transcriptional factors to DNA, and attracts histones, so the DNA-histone complex is more condensed, making it inaccessible to transcriptional factors. This means the gene is switched off
- What inhibits the transcription of genes?
Increased methylation of DNA or decreased acetylation of associated histones.
- Why can inhibiting gene expression contribute to the development of cancer?
If tumour suppressor genes get switched off, the rate of cell division increases which can result in tumour formation.
