Formation of Twins

Formation of Twins

15.5

Formation of Twins

Types of twins	Identical twins
Fertilisation	1 ovum fertilised by 1 sperm
Zygote formation	Formed from 1 zygote
Placenta	Share one placenta but have their own umbilical cord
Embryo division	Divide into two
Umbilical cords	2
Gender	Same sex
Genetic constitution	Identical
Physical characteristics	Identical
Fingerprints	Unique (different)

Types of twins	Siamese twins
Fertilisation	1 ovum fertilised by 1 sperm
Zygote formation	Formed from 1 zygote
Placenta	Share one placenta but have their own umbilical cors
Embryo division	Incomplete division
Umbilical cords	2
Gender	Same sex
Genetic constitution	Identical
Physical characteristics	Identical
Fingerprints	Unique (different)

Types of twins	Fraternal twins
Fertilisation	2 ovum fertilised by 2 sperm
Zygote formation	Formed from 2 different zygote
Placenta	Each has their own placenta and umbilical cords
Embryo division	Not divide into two
Umbilical cords	2
Gender	Same/different sex
Genetic constitution	Different
Physical characteristics	Different
Fingerprints	Unique (different)