MICROANATOMY

Detailed explanation-1: -To form identical or monozygotic twins, one fertilised egg (ovum) splits and develops into two babies with exactly the same genetic information. To form fraternal or dizygotic twins, two eggs (ova) are fertilised by two sperm and produce two genetically unique children.

Detailed explanation-2: -1 As the fertilized egg (called a zygote) travels to the uterus, the cells divide and grow into a blastocyst. In the case of monozygotic twins, the blastocyst then splits and develops into two embryos. In contrast, dizygotic (fraternal) twins form when two separate eggs are released and fertilized by two sperm.

Detailed explanation-3: -Identical twins form when one egg has been fertilised by one sperm and the zygote splits into two. This happens at the very earliest stage of development, when the zygote is no more than a cluster of a few cells.

Detailed explanation-4: -If one egg is fertilised by two sperm, it results in three sets of chromosomes, rather than the standard two-one from the mother and two from the father. And, according to researchers, three sets of chromosomes are “typically incompatible with life and embryos do not usually survive".