Twins happen by either a) the egg dividing into two once fertilised (identical twins) or b) 2 eggs being available and being fertilised by two different sperm.
Not sure on the genetic split, as each egg might have marginally different genetic material, but I'll leave that bit to biologists.
no subject
Twins happen by either a) the egg dividing into two once fertilised (identical twins)
or b) 2 eggs being available and being fertilised by two different sperm.
Not sure on the genetic split, as each egg might have marginally different genetic material, but I'll leave that bit to biologists.