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3. What is Down’s syndrome? Give its symptoms and cause. Why is it that the chance of having a child with Down’s syndrome increases if the age of the mother exceeds forty years?
3. What is Down’s syndrome? Give its symptoms and cause. Why is it that the chance of having a child with Down’s syndrome increases if the age of the mother exceeds forty years?
Biology | CBSE | Class 12 | NCERT Exemplar | Principles of Inheritance and Variation
3. What is Down’s syndrome? Give its symptoms and cause. Why is it that the chance of having a child with Down’s syndrome increases if the age of the mother exceeds forty years?

Solution:

The presence of an extra copy of chromosomal number 21 (9trisomy of 21) causes Down syndrome. 23 pairs of autosomes and 1 pair of sex chromosomes make up the karyotype. (There are a total of 24 pairs of chromosomes, or 47 chromosomes). Because ova are present in females since birth, and older cells are more prone to chromosomal non-disjunction, having a kid with Down’s syndrome increases if the mother’s age surpasses forty years.

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