Identical Twins Not So Identical

[Madame Butterfly 0]

Identical Twins Not So Identical

By Robert Roy Britt

LiveScience Senior Writer

posted: 08 July 2005

10:02 am ET

 

 

 

Identical twins are not quite as identical as once thought, according to a new study of DNA.

 

Life, it seems, changes everyone in unique ways.

 

One twin might get cancer while the the other is not susceptible, for example. Many identical twins clearly behave differently as they grow older, and some even grow to look less alike.

 

Such differences have to do not with the twins' identical DNA, which is the software of life, but in how genes express themselves, the research found. The differences stem from chemical modifications in the genes over the years.

 

These epigenetic effects, as they are called, are the result of chemical exposure, dietary habits and other environmental factors, the scientists believe.

 

The study is detailed in this week's Proceedings of the National Academy of Sciences.

 

Further investigation into the process might shed light on how cancers develop, said Ohio State University researcher Christoph Plass, a co-author of the report.

 

The idea that twins grow apart is not new.

 

In 2001, scientists documented that identical twins with different diets had corresponding differences in blood cholesterol measures. A study in 2002 found that identical twins tend to differ greatly in their levels of emotional distress, depending on how close each was to their mother or whether they attended church, among other social factors.

 

Research last year at Duke University found that identical twins both develop Alzheimer's by their late 70s only about 40 percent of the time. In many cases, one does and one does not.

 

Other studies have shown that the brains of identical twins look different upon close inspection of the wiring.

 

The new research, among the first to provide a detailed look at such differences at the genetic level, was led by Manel Esteller of the Spanish National Cancer Center in Madrid. The scientists studied 40 pairs of twins in Spain, Denmark and the United Kingdom, aged three through 74. The participants were surveyed on a range of health, exercise, eating habits and other lifestyle issues. Their blood was analyzed for epigenetic differences.

 

The youngest set of twins had the most identical genomes. Genetically, the oldest twins were the least alike.

 

Gene expression and behavior is altered by a process called methylation. Scientists think a better understanding of methylation could aid cancer research.

 

"One would expect identical twins to develop and express genes at the same levels, but in fact this changes over time," Plass said. "We think that methylation plays a genome-wide role in these changes."

[Theunicornhunter 2]

What suprises me about this article is that it is written as if this information is surprising. I guess for people that believe we are totally a product of genetic programming it is. I think it just shows that environment and life experience does also influence "who we are"

 

I shared an apartment with a set of twins in college - I could tell them apart fairly easily after a few weeks. I have cousins I never could tell apart- because I didn't see them often.

[mj 7]

I was in a program where I taught one half of a pair of identical twins. I saw both twins about a year later at a conference. The twin I taught had a look of recognition in his face, and his actions. Even when I ran in to them separately, I could tell from a distance whether it was the one I knew, or the one I did not know by how they responded to me. Even after I go to know the second twin, I never mistakenly called either the wrong name.

[Theunicornhunter 2]

I read somewhere that the incidence of twins is on the rise. It certainly seems like I see them everywhere.

 

I think by the time they get older and develop their personalities it may be easier to tell them apart - but I've had the opportunity to babysit some different twins in my life.

 

One set, I always had the parents tell me who had on which color shirt so I knew which one was which throughout the night. On one occasion big sister decided to undress the twins which I'll call Joe & Bob; I gasped "don't take their clothes off - I won't know who they are" She looked at me like I was really stupid and still looking puzzled said "well, one's Joe and one's Bob"

[Madame Butterfly 0]

Twins are on the rise to do the rise in need of 'assistance" with getting pregnant.

 

It's not a natural phenom, it's artificial.