I recently heard an article about epigenetics on the radio and decided to look into it further, and found how it offered revolutionary ideas to our understanding of inheritance. The findings of the Overkalix Study demonstrate the idea well.
This investigation was led by Marcus Pembrey and his colleagues. It was inspired by certain abnormalities in inheritance of genetic diseases such as Angelman Syndrome. Pembrey investigated the causes of death relative to ancestor’s nutrition during early life, overs three generations in a small, isolated locality in north Sweden called Overkalix.
Method:- a sample of around 300 was used, from births in 1890, 1905, 1920 and 1935. The selected individuals’ ancestry was traced back two generations and records of the village’s harvests and food prices were used to determine the likely diet of the paternal parent and grandparent.
Results:- it was found that when the paternal grandparents were restricted to a lean diet due to poor harvests during ages 9-12, their children and grandchildren had significantly lower diabetic and heart disease mortality than those whose grandparents had a rich diet ages 9-12.
Ages 9-12 in the paternal grandparents could have been their Slow Growth Period (SGP). This is when the body stops growing and prepares for puberty. Gamete production begins and environmental factors have a larger impact on the body.
The reason this correlation was only seen with the paternal grandparents must be due to Genomic Imprinting; the paternally inherited allele of a gene is expressed, while the maternal one is subdued. This also explains the odd inheritance patterns of diseases such as Angelman Syndrome.
We can also conclude that diet must somehow affect the production of the gametes if it is to affect genetic information in any way. What must happen here is epigenesis; a change in gene expression. A rich diet ages 9-12 means certain genes are ‘switched on’ (or off) so the offspring can best cope with a similar diet. And when these genes are passed on to a second generation (by the father), these individuals have an increased risk of dying from diabetes or heart disease. And the opposite can be said for the generation whose paternal grandparents had a lean diet ages 9-12.
Conclusion:- although the genetic material being passed on remains the same, this study has shown that change in gene expression (epigenesis) due to environmental factors, can affect things as serious as diabetic and heart disease mortality in offspring over two subsequent generations. Further research into epigenetics will contribute significantly to the continual advancement of medicine.