My wife is a sociable woman. Usually among the last persons to leave any gathering, she likes to talk to as many people as she can. So when she told me last Friday that we’d be going home directly after the services that evening, I was pleased. The job of unpacking the 99 cartons that had arrived from Jerusalem earlier in the week (a job still largely unfinished) had left us both tired. We needed to maximize our rest.
At last Shabbat evening’s service, as I reported in my Monday's post, our rabbi introduced a new convert to the congregation. “Oh, I must congratulate Karen,” said my wife, as we left the chapel. So after the blessing over wine and bread, my wife talked in turn to Karen and to each of her three children. And as usual, we were among the last to leave the building.
But one should see the possibility of a good outcome from any event that on its face seems unfavorable. There was indeed a good outcome of our leaving later than I had hoped, for I had a chance to talk to Karen's 85-year-old father, who had come with his wife and another daughter all the way from the state of Washington to attend his daughter’s presentation to the congregation.
White haired, blue-eyed, and rosy cheeked, he is the apotheosis of a beautiful old man. He walks with a cane but he is more active than I am. Twenty years ago, he retired from a senior administrative position in one of the national research institutes and then started a new career as a university lecturer. Among the courses he teaches is a graduate course in epigenetics. This is a relatively new field, so perhaps I can be excused for not having heard of it before. But I pushed the right button when I asked him about it, for he is passionately engaged in this field, and he was glad to give me a brief tutorial.
Our DNA is wrapped around a protein called histone, both of which are covered with tags. These tags constitute a second layer of structure, the epigenome, that shuts down some genes and activates others throughout the individual’s life. Whereas our DNA is fixed, our epigenome is flexible, reacting to outside influences, such as diet and stress. Epigenetics, then, is the study of the reactions that switch parts of the genome on and off and the factors that influence these reactions.
Karen’s father seemed most excited about epigenetic inheritance. The embryo’s epigenome is not built entirely from scratch because a small minority of epigenetic tags are passed down from generation to generation. This is an unexpected finding, because until recently it had been thought that the DNA that passes from parent to child is the sole agent of inheritance. So if, for example, starvation causes changes in a person’s epigenome, some of these changes, which regulate the expression of given genes, may be passed on to succeeding generations. The parent’s experiences can influence the expression of genes in the child.
I learned this while each of us was, so to speak, standing on one leg. I would have learned more from him had our conversation not been interrupted by his grandchildren, who were eager to get the old man home. It was good to learn something new. It was even better, indeed inspiring, to see an 85-year-old man so enthusiastic about his work.
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Epigenetics, as you describe it, is a fascinating development, because it mediates between two opposing poles of influence -- nature and nurture. Yes, we are dealt a favorable or unfavorable hand, one which will be transmitted to our posterity. But what we do with that hand will also influence those who come after us. I'm reminded of a saying which says, in effect, that life is a voyage in which the ship we sail and the weather we experience are givens that we cannot change. Nonetheless, much can be accomplished by adroit management of the sails, and of the helm.
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