How do you know that genes are the instructions that can tell our whole body how to grow and develop in life? They are like a recipe that creates each of us as unique individuals. We have two copies of each of our genes, one from our biological mother and the other from our biological father. That’s why we’re like our mom and dad.
Identical twins usually occur when the zygote splits in two during the first few days after fertilization. They are made from a single egg and a single sperm, so they share the same genes as each other. There is an opinion that the reason for the division of the zygote may be inherited, and this may be the reason why some families have several pairs of twins.
Because identical twins are descended from a single zygote, which in turn splits into two, they have exactly the same genes – the exact same recipe. They will both have the same colored eyes and hair and look the same. Homosexual twins are mostly of the same sex. they will both be girls or both boys. The twins of the same name are called monozygotic twins. This simply means that they came from the same zygote (mono means “one”). Heterogeneous twins are sometimes called dizigo twins (di means “two”, hence dizigous means two zygotes).
Earlier it was reported that most women produce one egg per month. From time to time females can produce more than one egg per month. Heterogeneous twins occur when a woman produces two eggs (in the same month) and the two eggs are fertilized by two different sperm.
Unlike identical twins, non-homogeneous twins do not share their genes with each other. They grow up together and have the same birthday, but only the other brothers and sisters. Non-identical twins can be girls or boys, or they can be one girl and one boy twins.