3. EPIXENÉTICA

https://www.thesciencehive.co.uk/stem-cells-and-gene-expression-a-level

Epigenetics

Epigenetic modification involves the addition or removal of chemical ‘tags’ onto DNA or histone proteins. These modifications are caused by environmental factors (such as diet, stress and smoking) and can occur from as early as when we are in the womb.

The addition or removal of epigenetic tags changes the structure of the chromosome, making it either more or less accessible to RNA polymerase, transcription factors and other proteins which are involved in transcription. The more open the structure of the chromosome, the more accessible it is to RNA polymerase - the gene is switched on. The less open the structure, the less accessible it is and transcription is reduced - the gene is switched off. The two main types of epigenetic ‘tags’ are methyl groups and acetyl groups.