What genetic condition is commonly associated with trisomy 21?

Trisomy 21 is a genetic condition that results from the presence of an extra copy of chromosome 21. This condition is most commonly known as Down Syndrome. The extra genetic material interferes with normal development, leading to the characteristic physical and intellectual features associated with this syndrome.

Individuals with Down Syndrome often exhibit distinct facial features, such as a flat facial profile, slanted eyes, and a single transverse palmar crease. Additionally, they may have a higher risk of congenital heart defects, gastrointestinal issues, and varying degrees of cognitive impairment. The prevalence of this trisomy and its associated traits underscores the relationship between chromosomal abnormalities and specific genetic conditions.

The other conditions listed in the question are caused by different genetic anomalies. Turner Syndrome is the result of a missing or incomplete X chromosome, Marfan Syndrome is linked to mutations in the FBN1 gene affecting connective tissue, and Klinefelter Syndrome involves the presence of an extra X chromosome in males. Each of these conditions has distinct characteristics that are unrelated to the chromosomal configuration seen in Down Syndrome.