
It is caused due to a gene mutation in a chromosome. Both mother and father contribute one each to form a single pair of chromosomes in a child, which creates the unique genetic code of a child. However, due to certain maternal or environmental factors, chromosomes may mutate and the baby can be born with an extra copy of chromosome 21.
Chromosomes are a bundle of genes which are inherited by the child from its parents. Chromosomes come in pairs, and our body needs just the right number of pairs for the development of the body. There are 23 pairs of chromosomes in all healthy individuals. It is due to this extra copy of chromosome 21 that a child develops the characteristic physical and developmental problems associated with Down syndrome.
There are three different types of Down syndrome:
In trisomy type, every cell in the body has three copies of chromosome no. 21 instead of two. This is the most common type of Down syndrome.
In the translocation type, each cell has a part or entire extra chromosome 21 which is attached to other chromosomes.
In this type, only some of the cells have an extra chromosome 21. This is a rare type.
Usually, Down syndrome in a baby is identified prenatally (while the baby is in the womb) through pregnancy screening tests. It is also possible that the doctor may suspect a case of Down syndrome at birth or during follow-up visits due to the characteristic physical appearance that occurs with the condition.
1. Characteristic physical appearance
Individuals who have Down syndrome have distinct facial features, such as:
Along with the myriad of characteristic physical appearances, children with Down syndrome also suffer from intellectual and developmental disabilities and may develop other health-related comorbidities.