For the John Templeton Foundation, I wrote about how epigenetics shapes our biological heritage beyond our DNA.
These changes are crucial to organizational development: most cells in our bodies have exactly the same genome, but epigenetic triggers have influenced which ones developed as skin or muscle or nerve cells. Changes in nutrition, exposure to toxins, infections or other stressors can also alter the epigenome to influence how organisms develop. Many epigenetic changes can even be passed on from parent to offspring, allowing a form of inheritance that occurs outside the genome. This means that some of the ways an organism develops are determined not only by the genes their parents and grandparents passed on, but also by the lives they lived.
Epigenetic change and inheritance can occur through several biochemical mechanisms. DNA methylation is one. It involves the addition of chemical groups to the surface of underlying DNA. This can block the proteins that would normally read certain genes, effectively switching them off. A few methylation patterns are passed on along with the underlying genes when egg or sperm cells are created. This means that a change due to a single environmental exposure can alter genetic expression across multiple generations.