World Down Syndrome Day 2024: Know The Causes Of This Condition

Down syndrome is a genetic condition that is usually caused by an extra copy of the twenty-first chromosome.

Most people have two copies of each chromosome, for a total of 46. People with Down syndrome have three copies of the 21st chromosome, for a total of 47.

Down syndrome is also called trisomy 21.

This does not typically run in families and is not caused by anything either parent did or did not do.

Some people can have ‘Translocation Down syndrome’ or ‘Mosaic Down syndrome,’ which are rare genetic variations of Down syndrome.

People with translocation Down syndrome can inherit the condition from an unaffected parent.

The parent carries a rearrangement of genetic material between chromosome 21 and another chromosome. This rearrangement is called a balanced translocation.

No genetic material is gained or lost in a balanced translocation, so these chromosomal changes usually do not cause any health problems.

However, as this translocation is passed on to the next generation, it can become unbalanced.

People who inherit an unbalanced translocation involving chromosome 21 may have extra genetic material from chromosome 21, which causes Down syndrome.

Like trisomy 21, mosaic Down syndrome is not inherited. It occurs as a random event during cell division early in foetal development.

As a result, some of the body's cells have the usual two copies of chromosome 21, and other cells have three copies of this chromosome.

Inputs By: Dr. Dipanjana Datta, BGCI Level II certified genetic counsellor at Renew Healthcare