What is Down's syndrome? Give its symptoms and cause. Why is it that the chances of having a child with Down's syndrome increases if the age of the mother exceeds forty years?

Explanation

Down.s syndrome is an autosomal human genetic disorder or syndrome that develops due to trisomy of chromosome 21. The individuals are aneuploid and have 47 chromosomes, Symptoms. Short stature, small round head, broad forehead, small ears, open mouth, projecting lower lip, protruded furrowed tongue, epicanthial-fold on either side of nose, short, flat bridge nose, short neck, short broad hands, short phalanges, space between first and second digits, broad palm with characteristic simian crease, finger tips with many .loops., mental retardation, retarded psychomotor development (loose jointedness), underdeveloped gonads and genitals, short life expectancy. Reason. Non-disjunction of chromosome pair 21 during meiotic division in ovum. Chances of such non-disjunction increases with age of mother (+40) because ova have developed in females since birth and the older cells become more prone to such abnormalities due to various physico chemical exposures.