<P> Zygosity is the degree of identity in the genome of twins . </P> <Table> <Tr> <Th> Common name </Th> <Th> Scientific name </Th> <Th> Zygosity </Th> <Th> Development </Th> <Th> Occurrence </Th> <Th> Identification </Th> <Th> Health </Th> <Th> Other </Th> </Tr> <Tr> <Td> identical </Td> <Td> monozygotic </Td> <Td> x </Td> <Td> x </Td> <Td> x </Td> <Td> x </Td> <Td> x </Td> <Td> x </Td> </Tr> <Tr> <Td> fraternal </Td> <Td> dizygotic </Td> <Td> x </Td> <Td> x </Td> <Td> x </Td> <Td> x </Td> <Td> x </Td> <Td> x </Td> </Tr> <Tr> <Td> half - identical </Td> <Td> x </Td> <Td> x </Td> <Td> x </Td> <Td> x </Td> <Td> x </Td> <Td> x </Td> <Td> x </Td> </Tr> <Tr> <Td> mirror image </Td> <Td> x </Td> <Td> x </Td> <Td> x </Td> <Td> x </Td> <Td> x </Td> <Td> x </Td> <Td> x </Td> </Tr> <Tr> <Td> mixed chromosome </Td> <Td> x </Td> <Td> x </Td> <Td> x </Td> <Td> x </Td> <Td> x </Td> <Td> x </Td> <Td> x </Td> </Tr> <Tr> <Td> superfecundation </Td> <Td> x </Td> <Td> x </Td> <Td> eggs are fertilized during different acts of intercourse </Td> <Td> x </Td> <Td> x </Td> <Td> x </Td> <Td> usage is practically equivalent with Heteropaternal Superfecundation, which occurs when two different males father fraternal twins, because though superfecundation by the same father is thought to be a common occurrence, it can only be proven to have occurred with multiple fathers . </Td> </Tr> <Tr> <Td> superfetation </Td> <Td> x </Td> <Td> x </Td> <Td> a woman gets pregnant again while already pregnant, resulting in multiple fetuses at differing developmental stages </Td> <Td> x </Td> <Td> x </Td> <Td> x </Td> <Td> x </Td> </Tr> <Tr> <Td> parasitic twin </Td> <Td> x </Td> <Td> x </Td> <Td> x </Td> <Td> x </Td> <Td> x </Td> <Td> by definition only healthy fully formed fetus </Td> <Td> x </Td> </Tr> <Tr> <Td> vanishing twin </Td> <Td> fetal resorption, twin embolisation syndrome </Td> <Td> x </Td> <Td> x </Td> <Td> up to 1 of every 8 multifetus pregnancies </Td> <Td> x </Td> <Td> by definition only healthy fully formed fetus </Td> <Td> chimerism, mosaicism </Td> </Tr> <Tr> <Td> polar body </Td> <Td> x </Td> <Td> x </Td> <Td> x </Td> <Td> x </Td> <Td> x </Td> <Td> x </Td> <Td> x </Td> </Tr> <Tr> <Td> conjoined twin </Td> <Td> x </Td> <Td> x </Td> <Td> x </Td> <Td> x </Td> <Td> x </Td> <Td> ranges from normal to compromised </Td> <Td> x </Td> </Tr> </Table> <Tr> <Th> Common name </Th> <Th> Scientific name </Th> <Th> Zygosity </Th> <Th> Development </Th> <Th> Occurrence </Th> <Th> Identification </Th> <Th> Health </Th> <Th> Other </Th> </Tr> <Tr> <Td> identical </Td> <Td> monozygotic </Td> <Td> x </Td> <Td> x </Td> <Td> x </Td> <Td> x </Td> <Td> x </Td> <Td> x </Td> </Tr>

How are twins created mono zygotic and dizygotic