A couple has twins, one is a boy and one is a girl. How do you know what kind of twins they are?
1 Answer
They are fraternal or dizygotic twins.
Explanation:
There are two types of twins possible:
1. Identical or monozygotic:
2. Fraternal or dizygotic:
To form identical twins, a single fertilised ovum splits into two and develops into two separate embryos with identical genetic codes (since the splitting takes place after the combination of DNA from sperm and ovum). In such a case, the twins are identical in every respect, including sex.
To form fraternal twins, two separate ova are fertlised by two separate sperms and develop into two separate embryos with different genetic codes. In such a case, the twins are not identical, though the possibility of both being of the same sex exists.
In the given case, since the twins are of different sex, they have to be fraternal or dizygotic twins.
