The range of fertility vs. sterility in Down syndrome individuals


Question Description:

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The range of fertility vs. sterility in Down syndrome individuals is not completely clear: Males have long been assumed to be sterile, although it’s possible that absence of children from Down syndrome men may be associated with lack of sexual activity, rather than aberrant sperm development, since cases of Down syndrome fathers have been documented; approximately 50% of Down syndrome females are believed to be fertile. For this problem, assume that all Down syndrome individuals are fully fertile and that chromosome segregation occurs at random, with each gamete getting at least one chromosome 21. 1) a Down syndrome male with a normal female? Express the answer as the ratio of Down syndrome children to normal children, using a colon and no spaces. For example, 1:6 would represent 1 Down sydrome to 6 normal. If only normal children would be produced, the answer would be 0:1. 2) a Down syndrome male with a Down syndrome female? Express the answer as the ratio of Down syndrome children to normal children, using a colon and no spaces. For example, 1:6 would represent 1 Down sydrome to 6 normal. If only normal children would be produced, the answer would be 0:1.

Answer

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