By BRINLEE VUOLA
Staff Writer
When you hear the term “identical twins,” what comes up in your mind? Most likely 2 people who look exactly the same, with flawless DNA and–if raised together–very similar personalities. But what if I told you that according to researchers earlier this year, new evidence suggests that identical twins’ genes are actually NOT totally identical?
Early this year, in an Iceland experiment of about 381 pairs of twins, only 38 pairs had the exact same genes. Most of the differences came from DNA and arose after birth, not during womb development. Over 39 of those not-so-similar pairs had about 100 differences in their genes.
In order to have twins conceived, 2 sperm cells go into an egg–or zygote–instead of the traditional 1 cell. After that zygote becomes an embryo, it splits into 2 different clumps of cells, making up the individual fetuses. The reason that most identical twins are completely identical is because those embryos split cleanly in half with the same amount of starting cells; situations where identical twins have any kinds of differences, big or small, are from an embryo splitting a bit unevenly. One single cell difference in 2 fetuses that are supposed to be identical, can change a lot of things about the DNA.
Changes in looks and DNA, just as changes in almost everything are, can be either major or minor depending on which exact traits and DNA strands are unique from one another. Of course, it won’t take away the title of “twins” from those siblings, since fraternal twins–twins who have similar DNA, born at the same time, but acquire different looks–exist too. But many people, including myself, have thought identical twins always have the same genes with no exceptions. This is definitely an interesting discovery that researchers will continue to build upon in the future.