What causes Down syndrome?
All people with Down syndrome contain an extra pair of chromosome 21 present in their all or some cells, regardless of their type of Down syndrome. This additional genetic chromosomal material affects development and leads to the characteristics associated with Down syndrome.
The cause of the presence of an extra full or partial chromosome is still unknown. Maternal age is considered the only factor that can increase the chance of having a child with Down syndrome resulting from mosaicism or nondisjunction. However, as the birth rates are higher in younger women, almost 80% of babies with Down syndrome are born to mothers under 35.
There is no definite scientific research that shows that the cause of Down syndrome is environmental factors or any parents’ activity before or during pregnancy. The additional full or partial copy of chromosome 21, which leads to Down syndrome, can originate from either the mother or the father. Around 5% of the cases have been tracked down to the father.
People with Down syndrome may face mild to severe cognitive delays. They also have some same physical traits like small stature, upward-slanting eyes, and an inability to gain muscle tone, although the severity of these degrees can differ. To understand this condition, it’s essential to know all of the possible causes of Down syndrome and its risk factors.
Trisomy 21
There are usually three types of Down syndrome, each has different causes, and trisomy 21 is the most common among these. In this condition (trisomy 21), a random error occurs during cell division. This error is termed as “nondisjunction.” Generally, each pair of chromosomes from the mother and father separate at conception to form one-half of the feotal’s chromosomes’ pair. While in trisomy 21, one of the pairs of 21st chromosomes does not get separated. This results in the three 21st chromosomes in the embryo instead of two, which replicates throughout development.