A 30-year-old woman has a 1 in 3,000 chance of giving birth to a child with trisomy 21; however, a 48-year-old woman has a 1 in 9 chance. Which statement is the most likely explanation for why a woman has a higher probability of giving birth to a child with trisomy 21 as she ages?
a. Older women are more likely to mate with older men, and the older the man, the older the sperm. Older sperm are more likely to experience a non disjunction event during meiosis.
B. Older women have older oocytes, and the older the oocytes, the greater the chance they will experience a nondisjunction event during meiosis.
C. Older women have lived longer and have an increased percentage of toxins and oxidative damage in their bodies. Because these are the major causes of trisomy 21, the likelihood of giving birth to a child with trisomy 21 increases.
D. Older women have older oocytes, and the older the oocytes, the greater the chance they will experience failure of cytokinesis during cell division.
Answer: B. Older women have older oocytes, and the older the oocytes, the greater the chance they will experience a nondisjunction event during meiosis.
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