What genetic alteration primarily causes Down Syndrome?

What genetic alteration primarily causes Down Syndrome?

• A. Deletion of chromosome 21
• B. Monosomy of chromosome 21
• C. Trisomy 21, where three copies of chromosome 21 are present
• D. Inversion mutations in chromosome 21

Answer: (C)

Trisomy 21 is the genetic alteration that primarily causes Down syndrome. In this condition, an individual has three copies of chromosome 21 instead of the normal two, which leads to the various physical and developmental characteristics associated with Down syndrome. This extra genetic material affects the way the body and brain develop, resulting in the hallmark features of the condition such as intellectual disabilities, distinctive facial features, and an increased risk for certain medical issues. The presence of a third copy of chromosome 21 disrupts normal development processes, which is why it specifically leads to Down syndrome. Other genetic alterations, such as deletions, monosomy, or inversions, do not account for the typical presentation of Down syndrome, as these involve missing or rearranged genetic material rather than an excess of chromosome 21. This excess is what is specifically linked to the manifestations observed in individuals with Down syndrome.

Trisomy 21 is the genetic alteration that primarily causes Down syndrome. In this condition, an individual has three copies of chromosome 21 instead of the normal two, which leads to the various physical and developmental characteristics associated with Down syndrome. This extra genetic material affects the way the body and brain develop, resulting in the hallmark features of the condition such as intellectual disabilities, distinctive facial features, and an increased risk for certain medical issues.

The presence of a third copy of chromosome 21 disrupts normal development processes, which is why it specifically leads to Down syndrome. Other genetic alterations, such as deletions, monosomy, or inversions, do not account for the typical presentation of Down syndrome, as these involve missing or rearranged genetic material rather than an excess of chromosome 21. This excess is what is specifically linked to the manifestations observed in individuals with Down syndrome.