Epigenetic Inheritance How Do Today's Events Impact on Future Generations?

The nurture vs. nature question and how much of who and what we are goes beyond DNA has always fascinated us. Is it possible we can directly influence what we pass on to future generations? How malleable is our identity?

In 2003, the Human Genome Project's (HGP), discovery of the blueprint of the body - man's genetic code entirely mapped out, all 3 billion letters of DNA - is considered by some to be the scientific discovery of the century or the "Holy Grail" of molecular biology. However, this discovery, as amazing as it is, is only the beginning.

"It's sort of like having the words in the dictionary, but you don't really what they mean. You can't put them into a sentence or a phrase or anything." -- Frank DiLorenzo, a stock analyst at S&P Equity Group in New York who covers the biotech industry.

Profit potential has and will determine the rate at which further discoveries are made based on the findings of the human genome project, and also whether those involved will be operating at full or optimum speed. In other words, if is ascertained that dandelions, crabgrass and/or some other worthless substance is the cure for most of what ails human beings, future discoveries will never see the light of day or even more likely the abundant weeds will be transformed into something none of us has ever heard of and so rare that multi-million dollar companies will have to hire experts to find and transform it to something the human body can tolerate. The public must never know the answer to whatever is making their life a living hell is what they spend a fortune to eliminate from their lives.

That said, the mapped out DNA sequence alone will not answer all the questions, no matter how much profit is potentially available. Epigenetics, the study of heritable changes in gene expression and regulation that have little to do with DNA sequence, may answer some of the following questions. Why is it that the Irish seem more prone to alcoholism? Why do certain ethnic groups manifest diseases exclusive to them? Tay Sachs? Sickle Cell Anemia? How could the same genetic abnormality lead to two very different diseases? Could it be that experiencing adverse social and environmental conditions have a direct impact upon the health of future generations? If genes are the fundamental basis for human behavior, how do cultural factors influence the selection and hence, survival of particular genes?

Jewish children, born after the Holocaust were found to suffer from an abnormal level of stress relative to the wider population. It was assumed that this was the result of parents passing along their experiences of surviving the Holocaust. Years later it was confirmed that it was not hearing stories of the Holocaust rather the event of the Holocaust itself triggered changes in the parents genes, and passed on to future generations.

Apparently, the events and environment we are exposed to can alter and incorporate what we've experienced into our DNA, meaning the Holocaust, war, the depression etc. regarded as one time occurrences, lives on in the genes of its descendants.

Epigenetic inheritance provides a "rapid mechanism by which [an organism] can respond to the environment without having to change its hardware." Epigenetic patterns are so sensitive to environmental change that, in the case of the agouti mice, they can dramatically and heritably alter a phenotype in a single generation.

The epigenetic or biochemical switches that can turn genes on and off and the events and environmental factors which influence those switches has as much to do with how an organism develops and the inter-generational impact of the genes as the actual DNA sequence itself.

Recently, genes in the brains of suicide victims manifested epigenetic markings scientists believe were indicative of child abuse and were different from the brains of men who had not committed suicide. It would be interesting to see if those same markings showed up in their offspring.

"Our data are merely consistent with the hypothesis that early life events can alter the epigenetic status of genes that mediate neural functions, and thus contribute to individual differences in the risk for suicide," conclude the authors.

Children who were conceived via invitro fertilization were up to four times more likely to develop certain genetic abnormalities and that this was due entirely to the fact that the egg was exposed to environmental change i.e. being removed from the womb and placed in a Petri dish or test tube for fertilization by sperm from the prospective father. Epigenetic inheritance also may be the reason that human cloning is all but impossible.

Nurture and nature may be indistinguishable.

Indeed, Jirtle suspects that epigenetic inheritance may be behind some of the toughest diseases to crack, such as autism, bipolar disorder and schizophrenia.