What genetic condition results from an abnormality in the twenty-first pair of chromosomes?

Down syndrome, also known formally as trisomy 21, is the genetic condition that arises from an abnormality in the twenty-first pair of chromosomes. Typically, individuals have two copies of each chromosome, but those with Down syndrome have an extra copy of chromosome 21, resulting in three copies instead of the usual two. This genetic anomaly leads to a range of developmental and physical characteristics associated with the condition.

Individuals with Down syndrome often display distinct facial features, developmental delays, and a variety of health issues. Early intervention and specialized therapies, including music therapy, can effectively improve the quality of life and developmental outcomes for these individuals. The identification of Down syndrome usually occurs through prenatal testing or, shortly after birth, through clinical observation.

Other conditions mentioned do not relate to the twenty-first pair of chromosomes. Asperger's syndrome, now classified under the Autism Spectrum Disorder (ASD), does not have a direct genetic anomaly like Down syndrome. Similarly, Tourette syndrome is a neurodevelopmental disorder characterized by tics and has a different genetic basis. Learning disabilities can arise from various causes, including environmental factors and different genetic influences, but are not associated specifically with an abnormality in chromosome 21.