What is the chromosomal anomaly responsible for Down Syndrome?
Answer and explanation
Correct answer: A. Trisomy 21
- Step 1: Down syndrome is an autosomal aneuploidy caused by meiotic non-disjunction of chromosome 21. Step 2. The karyotype has 47 chromosomes with three copies of chromosome 21 (trisomy 21). Answer: Trisomy of chromosome 21 (47, +21). Why not the others: Monosomy 21 is lethal in utero; trisomy 18 is Edwards syndrome; deletion of 5p is Cri-du-chat syndrome.
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