Having two children through one pregnancy means the children are twins. Twins can be one of the two types identical or fraternal. Read out what is the difference between identical and fraternal twins.
Twins having the same features or genders do not mean that they are identical twins. There are many factors that affect the type of twins. The basic and the most important one is the fertilization of the egg. Identical and fraternal twins can be differentiated the following way.
When the born twins are monozygotic then it means they are identical. Monozygotic means one fertilized egg. Mono meaning one and zygotic meaning fertilized egg. If only one egg is fertilized and that egg later split into two embryos then identical twins are born.
One other thing that is important is that identical twins are always of the same gender example twin boys or twin girls.
The base of monozygotic twinning is not known yet and it is considered to be a divergence in the typical zygote procedure. Identical twinning is not a hereditary trait.
The identical twins have same DNA structures. They are not bound to have identical faces but there is a 25% chance that if they face each other while developing in the womb then they will be a reflection of each other.
When the born twins are dizygotic then they are fraternal twins. Fraternal twins are born through the normal zygote procedure. Meaning that two eggs are fertilized during pregnancy and both eggs forms two different and independent embryos. These embryos then form separate babies or fraternal twins.
These twins are like any other siblings with different DNA and they may or may not have the same gender. Most twins these days are fraternal twins.
Fraternal twins are a hereditary trait and can be effected by procedures.