Down Syndrome :Genetic Defects and Risk of Inheritance

Down Syndrome, also known as Trisomy 21, is one of the most common genetic disorders, characterized by the presence of an extra copy of chromosome 21. This condition results from different types of genetic defects, each with its unique mechanism and associated risk of inheritance. Understanding these genetic variations is crucial in assessing the likelihood of Down Syndrome occurring in families and for providing appropriate genetic counseling.

The three major subtypes of Down Syndrome - Trisomy 21 (Nondisjunction), Translocation, and Mosaicism - have distinct genetic profiles. Trisomy 21, the most common form, usually occurs as a random event during the formation of reproductive cells, with an increased incidence related to maternal age. Translocation Down Syndrome, while less common, carries a higher risk of inheritance, especially if one of the parents is a carrier of a translocated chromosome. Mosaicism, the rarest form, involves a mixture of cells with different chromosomal compositions and generally represents a lower risk of inheritance.