Explain how DZ and MZ twins are formed. Include a discussion of ethnic variations and factors that increase the chances of having twins
What will be an ideal response?
Answer: DZ twins result when the female releases two eggs instead of one and each is fertilized with a sperm. MZ twins result when a zygote is formed and it divides. DZ twins are more common among Africans and least common among Asians. MZ twins are not more common in some ethnic groups. The chances of having DZ twins increase if they run in the family, if the person is in good health and if the mother is older. None of these variables predicts MZ twins.
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