People with Down's syndrome have A) 45 chromosomes. B) 46 chromosomes. C) 47 chromosomes. D) No X chromosomes.

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Down's Syndrome is known as trisomy 21. That indicates an additional chromosome at pair 21. Therefore, people with Down's Syndrome are technically 2n+1 or contain 47 chromosomes. This occurs more often in mothers over the age of 35 having children. Women are born with their eggs in their ovaries and the older the woman...

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Down's Syndrome is known as trisomy 21. That indicates an additional chromosome at pair 21. Therefore, people with Down's Syndrome are technically 2n+1 or contain 47 chromosomes. This occurs more often in mothers over the age of 35 having children. Women are born with their eggs in their ovaries and the older the woman is, the longer those eggs have been exposed to environmental agents that could potentially damage those eggs. Down's Syndrome occurs in 1 out of 733 births. Older fathers too, can sometimes contribute to the risk of having a child with this condition.

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