Question

A couple has twins, one is a boy and one is a girl. How do you know what kinds of twins they are?

Answer 1

Twins are two offspring that are produced from the same pregnancy. They can be of two types- monozygotic or identical and dizygotic or non-identical.

Complete answer:
Dizygotic twins also known as fraternal or non-identical twins are the most common type. They occur when two fertilized eggs are implanted on the uterus at the same time and these two eggs are independently fertilized by two separate sperms giving rise to two zygotes.

Dizygotic twins share fifty percent similarity of each other’s genes and may or may not look similar. Monozygotic twins occur when a single egg is fertilized to form a zygote and the zygote then divides to give rise to two different embryos. Monozygotic twins are rare and they are almost genetically identical to each other. They are always of the same sex and look similar to each other.

To determine what kind of twins for a couple who has twins, one boy and one girl we need to carry out analysis of their DNA. If the DNA from both of them almost matches then they are said to be monozygotic twins whereas if the analysis matches fifty percent with one another they are said to be dizygotic twins.

Note: Apart from these two typical kinds of twins there are few unusual twinings such as bipaternal twins where the twins are said to be mixed having different ethnic and racial features, monozygotic twins of different sexes, semi identical twins and mirror image twins.