How Are Fraternal & Identical Twins Different?

Because of advances in medical technology, there has been an increase in twin births in recent decades. There are two separate typs of twins: fraternal and identical. Both types are different from one another.

Fraternal twins, which are often known as “non-identical twins,” generally occur when two separate eggs become fertilized by two different sperm cells and both implant into the wall of the uterus at the same time. The eggs form two separate zygotes, which leads to fraternal twins being referred to as “dizygotic” as well. Fraternal twins might look very similar, but often as they age they will begin to look different. Fraternal twins that have parents of mixed racial origins can even vary in their skin color. Fraternal twins typically do not have the exact same chromosome profile, although there is a small chance that this will be the case.

Identical twins come about when one egg is fertilized and implants in the wall of the uterus. The zygote then divides itself into two separate embryos. The two embryos develop into two separate babies who share the same womb. For this reason, identical twins are referred to as monozygotic twins. Identical twins sometimes share a single placenta, which can create a variety of complications with the pregnancy. Identical twins are genetically identical, and they are almost always the same gender. In some very rare cases, however, one of the zygotes might mutate and actually create identical twins that are of differnt genders. Identical twins look alike, although certain fine details, such as fingerprints, will be different. As they get older, identical twins also start to look less and less like one another because of external influences and lifestyle choices. Identical twins often show similar mannerisms, interests, and personality traits. In some instances identical twins might become “mirror twins” - identical twins with opposing features. In this instances, one might be right-handed while the other might be left-handed, for example. Mirror twins are extremely rare.