What makes Ashley and Mary-Kate Olsen not identical twins?
Identical twins can be born in separate sacs, which may seem like 2 eggs fertilized. The ONLY way to tell identical twins is DNA testing. My identical twin girls were born in separate sacs, one is taller, one has a more narrow face (a phenomenon in 100 percent of 100 identical twins study done in the 70’s), and their freckles are not in the same places. I believe MK and Ash are identical.
Ashley and Mary-Kate Olsen are not identical twins, they are fraternal twins. Identical twins occur when a single fertilized egg splits and forms two identical fetuses. Fraternal twins occur when two eggs are fertilized and develop into separate fetuses at the same time. There are several ways to tell if twins are identical or fraternal. The most certain is by zygosity determination, where the DNA of each is compared. Identical twins share identical DNA, fraternal twins do not.
I am pregnant with twins now. During an early sonogram, they told me immediately that I was having fraternal twins because the babies had two sacs and two placentas. They told me this way before they could even tell the babies’ sex, but they were right-I am having a boy and a girl so they are obviously fraternal. In the vast majority of cases, identical tw ins share one placenta and if they don’t, it’s pretty rare for them to have separate sacs AND seperate placentas. It could happen but it’s rare. If MK and A say they are fraternal they probably are- their parents were probably informed of this before they were born and for all anyone knows, maybe they did have genetic test done already. Just because they look identical doesn’t mean that they are. ALL of the Olsens look exactly alike and many siblings who aren’t even twins look a lot alike.
Actually, the earlier a fertilized egg separates to create twins, the more likely the twins will develop separate sacs…sometimes even separate placentas (http://multiples.about.com/cs/funfacts/a/twinzygosity.htm). Conjoined twins are at the opposite of that – splitting or starting to split very late, or split and then fuse. Then, there are chimeras where two separate fertilized eggs fuse to form one individual (watch “I Am My Own Twin” on Discovery Health), with DNA from both eggs intermingled in the body. I read an article where the Olsen twins mom stated that the girls couldn’t be identical because they were in separate sacs. I have never found an article where the mom states that the twins were genetically tested. If anyone has, please supply a link as I would love to read it.
