Define dizygotic twins. Summarize the genetic and environmental factors that increase the chances of giving birth to them
What will be an ideal response?
Answer: Dizygotic, or fraternal, twins are the most common type of multiple offspring. Fraternal twins result from the release and fertilization of two ova. Genetically, they are no more alike than ordinary siblings. Older maternal age, fertility drugs, and in vitro fertilization are major causes of the dramatic rise in fraternal twinning and other multiple births in industrialized nations over the past several decades. Currently, fraternal twins account for 1 in about every 33 births in the United States. Fraternal twinning occurs in 6 to 9 per 1,000 births among Asians and Hispanics, 9 to 12 per 1,000 births among white Europeans, and 11 to 18 or more per 1,000 births among black Africans. Dizygotic twinning occurs more often among women whose mothers and sisters gave birth to fraternal twins, suggesting a hereditary influence through the female line. Incidence of fraternal twinning rises with maternal age, peaking between 35 and 39 years, and then rapidly falls. It is more likely with each additional birth and with fertility hormones. Fraternal twinning occurs less often among women with poor diets and more often among women who are tall and overweight or of normal weight as opposed to slight body build.
What will be an ideal response?
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A. Europe B. The United States C. South America D. Africa