What is the difference between identical and fraternal twins?
Fraternal twins are the result of the fertilization of two ova by two sperm, so they will develop in the same mother at the same time. They are really like two regular brothers, but they are born together. They share the same genetic charge as any other siblings. On the contrary, Identical twins are the result of one ova fertilized by one sperm. The egg divides, creating two people with the exact same genetic charge, they are physically-wise the same person. Of course they will develop differently psicology-wise. This is why fraternal twins can be of different gender, while identical twins are always the same gender. Fraternal twins can be alike, but not necessarily (in fact they are sometimes very different), but identical twins will look exactly the same. Physical differences can be developed in time between identical twins, for instance if one of them plays lots of basketball and the other is lazy, one can grow taller than the other.
Twins in one of every three sets of twins are identical. Because they came from a single fertilized egg that split into two eggs, identical twins have the same genes. They are always the same sex. Other twins are fraternal. They develop from 2 different eggs and 2 different sperms and do not have identical genes. They may or may not be the same sex. Your healthcare provider may use ultrasound during the first trimester to try to find out if twins could be identical. He or she will check for 1 or 2 amniotic sacs or placentas. After the babies are born, healthcare providers can use DNA testing to find out if twins are identical.
