Question

What is the chromosomal abnormality that causes Down’s syndrome?

Answer 1

The chromosomal abnormality that causes Down’s syndrome is trisomy of chromosome 21. This means there are three copies of chromosome 21 instead of the usual two, resulting in 47 chromosomes in the affected individual. This abnormality occurs due to non-disjunction during gamete formation. Babies with this condition show characteristic physical features and mental retardation.