Epigenetics is the study of the changes that happen to the expression of genes without modifying the actual sequences within the gene.
Epigenetic changes interfere with the usual function of a DNA sequence, such as by preventing it from being transcribed or by exposing it when it would typically be hidden - essentially controlling if and how a gene works in the organism.
In most cases, epigenetic changes involve the addition of a methyl group (one carbon joined to three hydrogens) to the DNA structure; a change to a protein called a histone that keeps the DNA wrapped up tight; or use of non-coding RNA fragments to change the reading of a gene.
What epigenetic changes do
That means lifestyle factors can have a long term impact on genes, influencing their expression not just later in life but potentially transferring the gene's control settings to future generations through affected sex cells.