How are twins form in fertilisation?
Answers
Twins are formed when one egg is fertilized by one sperm which divides into two separate embryo.
Identical twins form when a fertilized egg formed by one sperm divides into two halves.Identical twins look exactly same, have same genes and usually of the same sex.Non-identical or fraternal twins form when two eggs are fertilized and both by two separate sperms.Fraternal twins can be of same or opposite sex, don't look exactly like each other and have different genes.And also there are conjoined twins which occur in extremely rare cases.Just like identical twins they look alike, share same genes and are of the same sex but during the spilt ,the embryo doesn't separate fully after fertilization.The developing embryo starts to split into identical twins for the first few weeks and then stop before the process completes.And so two babies are formed but attached to each other. conjoined twins don't survive many days.