Epigenetics is the study of the heritable chemical modifications to DNA or DNA-binding proteins (histones) that do not change the DNA base sequence itself, and that control whether genes are expressed.

The epigenome is a layer of chemical tags that cover the DNA-histone complex.

The epigenome affects gene expression by modifying the shape of the DNA-histone complex to either compact genes (keeping them switched off) or make them accessible (keeping them switched on).

Epigenetic inheritance is the transmission of information from parent to offspring without changes to the DNA sequence, often via chemical tags.

For example, gestational diabetes can cause epigenetic changes in the fetus due to a greater exposure to glucose, increasing the likelihood of the child developing the condition too.

Abnormal activation or silencing of genes due to epigenetic alterations can contribute to disease development.

Epigenetic therapy be used to treat diseases using drugs to modify histone acetylation or DNA methylation, potentially reactivating silenced genes.

RNA interference is a process where small RNA molecules inhibit gene expression by destroying messenger RNA before translation.

siRNA guides enzymes to mRNA, pairing bases with mRNA and allowing the enzymes to cut mRNA. This inhibits translation and gene expression.

Chromatin is the complex of negatively charged DNA coiled around positively charged histone proteins in eukaryotic cells.

It allows DNA to coil tightly to fit in the nucleus.

By altering the structure of chromatin, remodelling can make genes more or less accessible for transcription.

This allows cells to control which genes are active, influence cell function, and respond to environmental signals.

Histone acetylation is the addition of acetyl groups to the histone molecules, reducing their positive charge. This cause looser DNA coiling and enables gene transcription.

Histone deacetylation is the removal of acetyl groups from histone molecules, making them more positively charged. This increases the compaction of chromatin, and makes it harder for transcription factors to access DNA and preventing transcription.

Histone methylation involves adding a methyl group to histone proteins.

This causes the DNA to coil more tightly due to the attraction of proteins that condense chromatin. This makes DNA inaccessible to transcription factors, preventing them from binding and reducing gene transcription.