Which of the following statements about Down syndrome is/are true? Select one: a. A child with Down syndrome has 47 chromosomes instead of 46. b. Down syndrome occurs in one out of every 900 births. c. More children with Down syndrome are born to mothers over the age of 35. d. All of these. e. Symptoms of a child with Down syndrome include specific facial features.
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Step 1: Down syndrome is caused by trisomy of chromosome number 21, where instead of the normal two chromosomes, there are three chromosomes present. Show more…
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An individual with Down syndrome has three copies of chromosome 21. Would all children of an individual with Down syndrome also have Down syndrome? Select one: a. No, only 50 percent of the eggs or sperm formed would have an extra copy of the chromosome. b. No, only 25 percent of the eggs or sperm formed would have an extra copy of the chromosome. c. No, only 75 percent of the eggs or sperm formed would have an extra copy of the chromosome. d. Yes, all children would also have three copies of chromosome 21.
Adi S.
1. Familial Down syndrome is caused by a Robertsonian translocation involving chromosome 21. A carrier, who is unaffected, is phenotypically a normal carrier of the translocation and have 45 chromosomes. Their family members, who have Down syndrome, have 46 chromosomes, but one of these chromosomes is the translocation that has an extra copy of the long arm of chromosome 21. There is no reason to suspect that a carrier's spouse has any chromosomal abnormalities. For the statements below, what is true/false? Explain. a. a carrier has 47 chromosomes. b. a carrier has 46 chromosomes. c. a carrier has 45 chromosomes. d. a carrier's wife has 47 chromosomes. e. a carrier's wife has 45 chromosomes. f. a child with familial Down syndrome has 47 chromosomes. g. a child with familial Down syndrome has 45 chromosomes.
Madhur L.
What type of chromosomal abnormality leads to the phenotype known as Down syndrome? a) trisomy 21 b) monosomy 21 c) monosomy 22 d) trisomy 22 e) disomy 21
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