Down syndrome or trisomy 21 is a genetic disorder.
In this condition, chromosome 21 is repeated thrice instead of twice in a normal individual.
It occurs due to the non-disjunction of chromosomes. Non-disjunction refers to the inability of the sister chromatids to separate at the time of cell division.
Children suffering from this disorder face difficulties in learning to talk.
A child with Down syndrome generally starts to talk around 16 months of age.