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Monday, 11 February 2013

Can our parents' experiences change our genes?


We all know that the DNA we're born with doesn't change throughout our entire lives, except does it?
Epigenetics is the study of changes in gene activity that do not involve alterations to the genetic code but still get passed down to at least one successive generation. It's thought to be a way in which environmental experiences influence how genes are expressed. This is done using chemical tags (or epigenetic marks) attached to DNA which can turn certain genes on and off. The most common of these tags are a methyl group, when it attaches to our DNA it blocks the proteins and therefore turns that specific gene off.
It's thought that between each generation the epigenetic marks are erased (in cells called primordial gene cells, the precursors to sperm and eggs). This 'reprogramming' allows all genes to be read afresh for each new person. This process is fairly efficient in resetting genes, however some tags manage to escape and therefore pass on to the offspring.
Understanding this mechanism could lead to advances in adult diseases linked to the build up of deviant epigenetic marking such as cancers and aging cells.
How exactly can our environment affect our genes? studies on a rat pup's epigenome show that methyl groups silence the GR receptor in the pup's brain cells and the affection shown by the mother during the pup's first weeks have a significant effect on the pup's DNA. Strong nurturing signals remove the methyl groups and activate the GR gene. This epigenetic pattern remains even when the pup becomes an adult and the gene enables the rats to cope well with stress later on in their lives.

Other animal studies focus on how our diet can change our epigenome.They show that a diet deficient of methyl-donating foods during late fetal/ early postnatal development caused under-methylation of the genome. When certain genes such as the agouti gene are completely unmethylated, the mouse is yellow in colour, obese and prone to diabetes and cancer. However when pregnant yellow mice were fed a methyl-rich diet, their pups were brown and healthy and remained so for the rest of their lives.
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