January’s issue of National Geographic is all about twins. I’m all over it. There are some amazing portrait series. And there is also the main article which is fascinating.
Epigenettics is the study of heritable changes in gene expression caused by mechanisms other than changes in the DNA sequence. Epi comes from the Greek, meaning over, above, outer.
First you have to hear about the “Jim Twins“. Identical twins boys raised apart. They were both named Jim by their adoptive parents. When they were reunited at the age of 39 they learned about some startling similarities in their lives:
- growing up they both had dogs named Toy
- they both married a woman named Linda and then divorced her.
- their second wives were both named Betty
- they named their sons James Alan and James Allan
- they both were part-time sheriffs, enjoyed carpentry projects, drank Millar Lite, smoked Salem cigarettes and suffered from sever headaches.
Wow!
When scientists compare how likely identical twins are to share a given trait to how likely fraternal twins are to share a given trait, scientists can determine how much of the difference is due to genetic variation. For example, differences in people’s heights is 80% due to heredity.
However, epigenetic studies shows that environment can affect gene expression. Studies in rats show that stress during pregnancy can lead behaviour problems later on. Other epigenetic changes are random.
So, some of it we can control, sort of, and most of it we can’t, yet. Some scientists are working on a process called DNA methylation which can make gene expression weaker or stronger. A group of scientist are trying to looking for epigenetic “tags” in twins with autism (there is a very interesting story of male twins with autism in the article). This would help scientists understand how and why children with the same DNA could have such different degrees of the same trait, such as autism. These studies are in the early stages but seem very interesting. There is a story in the article about two identical boys on the spectrum. One is very high functioning while the other was non-verbal but has begun to speak a little.
Epigenetics is also scary. It renders the nature vs. nurture debate almost moot as they are so intertwined. This means our (and our parents’) behaviour and exposure to toxins or trauma can negatively affect our children and grandchildren. And we only control some of it; like diet, smoking or drinking excess amounts of alcohol,
The study of twins has helped scientists to understand a lot about epigenetics. I find it fascinating that one twin can have a gene expressed while the other doesn’t, or one can have a gene expressed to a greater or lesser degree.
Of course having identical twins I was all over this article as well Erin! Fasinating stuff indeed! I can’t wait to see how Thatcher and Tanner develop as identicals – I see differences now but in some areas they are so the same it is crazy!
I’ve always had a fascination with twins… not that I wanted to be the mother of multiples, but it’s all amazing to me. Even double-yolk eggs make me kind of giddy for some reason… I should probably pick up the National Geographic issue, when I see it!
I had just passed by the issue of National Geographic yesterday that was displayed in a store window. I was thinking I should pick it up. I’m amazed at the example of the brothers you’ve mentioned. Now I will definitely go back and get this issue!