When we were born in 1961, our parents, Jean and Butch Sullivan, were told we were fraternal because there had been two separate amniotic sacs and placentas. Identical, or monozygotic, twins develop from one zygote, which splits and forms two embryos. Fraternal or dizygotic, twins develop from two different eggs, each fertilized by its own sperm cell. Scientists used to think only fraternal twins developed in separate sacs, but I learned that has changed. It is now known if the egg split happens early before the sac has started to form, each zygote will develop its own sac and placenta. Babies that might appear to be fraternal twins could actually be identical twins.
“Could Rosemarie and I be identical twins?” I wondered. “Was there any scientific way to tell?”I discovered there was. My husband, Al, and I own ARCpoint Labs of Reading, 2208 Quarry Dr. in West Lawn. Through my work there, I learned of a DNA Twin Zygosity test performed earlier this year on 14-year-old twin sisters. These twins reminded me of Rosemarie and myself. They appeared identical but had been told they were fraternal. The test proved they were indeed identical. But what would it say about us?
We waited eagerly for our results. And then, we got the definitive answer. “We are identical!” Rosemarie and I now can say without hesitation. I was promoting ARCpoint’s DNA testing with the slogan “Who’s your daddy?” But I am starting a new campaign “I am an identical twin, and I can prove it!”
By Annmarie Sullivan Dallao
ARCpoint Labs of Reading