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Last Updated on April 3, 2023 by Shabnam Sengupta
Down syndrome is a major contributor to intellectual disability, and individuals with this condition often experience a range of health issues, such as congenital heart diseases (CHD), Alzheimer’s disease (AD), leukemia, cancer, learning and memory difficulties, and Hirschsprung disease (HD). In fact, millions of people around the world have down syndrome and its associated health concerns. In this article, we will discuss whether down syndrome is always inherited from parents and how people inherit it.
Is down syndrome always inherited?
Not exactly. Most cases of down syndrome are not hereditary. People inherit the condition only in some cases. According to the National Down Syndrome Society, all the 3 types of down syndrome are genetic. However, only about 1 percent of the cases are hereditary. Trisomy 21 (nondisjunction) and mosaicism are not hereditary. However, in one-third of the instances of down syndrome caused due to translocation, there is a hereditary component.
How can down syndrome be inherited?
People don’t usually inherit down syndrome from parents. A mistake in cell division before conception or during the early development of the foetus causes it. Only a small percentage of people inherit the condition, where the cause of the condition is translocation, a specific type of chromosomal abnormality. The translocation of down syndrome can pass from parent to child. Translocation occurs when a part of chromosome 21 breaks off and attaches to another chromosome. Suppose this translocated piece of chromosome 21 is attached to chromosome 14. In that case, it can result in down syndrome if the affected individual inherits this chromosome arrangement from one of their parents.
However, the number of children with down syndrome due to translocation is very less, and only some of them inherit it from one of their parents.
When balanced translocations are inherited, the mother or father has some rearranged genetic material from chromosome 21 on another chromosome but no extra genetic material. This means he or she has no signs or symptoms of down syndrome but can pass an unbalanced translocation on to children, causing down syndrome in the children.
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