What is Down Syndrome?

What is Down Syndrome?

What exactly is Down Syndrome? What makes people with Down Syndrome different than those without Down Syndrome? What makes them the same? What causes Down Syndrome?  What do I do if someone close to me has Down Syndrome? These are often questions that people often ask when they first encounter Down Syndrome.

According to the National Down Syndrome Society, or NDSS, nearly one out of 600 babies born in the United States is born with Down Syndrome. This makes Down Syndrome the “most common chromosomal condition” (What is Down Syndrome, n.d.). If we go by the approximate numbers, each year around 6,000 babies are born with Down Syndrome (What is Down Syndrome, n.d.).  

Down Syndrome had been touched on in different works of art and literature for centuries but it wasn’t until 1866 when a physician, John Langdon Down, published a description of a person with Down Syndrome that the condition was given an official name.  Significantly later in 1959, Down Syndrome was found to be a chromosomal disorder by a physician named Jerome Lejeune. This led to a multitude of advances in Down Syndrome research.

In a normally developing cell nucleus, each parent contributes to half of the 23 chromosomes. Down Syndrome is a chromosomal condition where an individual has a “full or extra copy of chromosome 21” (What is Down Syndrome, n.d.).  

There are three types of Down Syndrome: trisomy 21, mosaicism, and translocation. 95% of those with Down Syndrome has Trisomy 21. Trisomy 21 happens before or during a gamete formation where the spermatocyte and oocyte fails to divide properly during meiosis causing there to be three copies of chromosome 21 instead of the usual two (What is Down Syndrome, n.d.).  The second type of Down Syndrome is relatively rare, making up only 1% of all people with Down Syndrome. It is called Mosaic Down Syndrome. Mosaic Down Syndrome is when a person only has some cells with an extra chromosome 21 and others developed without the extra chromosome (Mayo Clinic, 2018). Therefore in this kind of Down Syndrome, some of the cells have 46 chromosomes and others have 47(What is Down Syndrome, n.d.).  Last but not least, the third type of Down Syndrome is Translocation. Translocation is where some of the chromosome 21 attaches itself, either fully or partially, to another chromosome, usually chromosome 14 (Mayo Clinic, 2018).

Because of this genetic difference and changes in development, there are specific phenotypic characteristics that are associated with Down Syndrome such as “low muscle tone, small stature, an upward slant to the eyes, and a single deep crease across the center of the palm” (What is Down Syndrome, n.d.).  However, each person with Down Syndrome is a unique individual with quirks and interests of their own. Additionally, although they may seem different from us in certain ways, they still experience the same emotions that we do.

How do I know if my baby or someone close to me is born with Down Syndrome? Before a baby is born a mother can take two different types of tests for Down Syndrome.  One is a prenatal screen that only provides the possible estimate of the mothers’ chances of having a baby with Down Syndrome (What is Down Syndrome, n.d.). The second is a diagnostic test performed during the second trimester that can provide a definitive diagnosis of Down Syndrome (What is Down Syndrome, n.d.). At birth, Down Syndrome can be diagnosed through the presence of physical traits characteristic of those with Down Syndrome. In order to confirm whether or not a child has Down Syndrome, a doctor may analyze the chromosomes using a karyotype or a chromosomal analysis.

At this moment, scientists are still unsure of the cause of Down Syndrome. However, what is known is that only 1% of all cases of Down Syndrome has a hereditary component (What is Down Syndrome, n.d.). Scientists have a long way to go in knowing everything about Down Syndrome but they are finding treatments to improve the lives of those with Down Syndrome. The treatment largely consists of therapy, but research is still needed for the expansion of the success of such therapies.   

A genetic component is what makes people with Down Syndrome different than those without the condition. However, besides the extra chromosome in their DNA, people with Down Syndrome are the same as any person out there. Even though many people with Down Syndrome also have a mild to moderate cognitive disability or intellectual disability (Mayo Clinic, 2018), they possess diverse talents as well. People with Down Syndrome are a part of our community and shouldn’t be treated differently because of something they were unable to control. They are our friends, our co-workers, our family, our classmates, and our mentors.  If someone you encounter has Down Syndrome, treat them as anyone should be treated: with respect and dignity. With a little more understanding and a lot more love, step by step, a better world can be created to encompass all people, one extra chromosome or not.



Mayo Clinic: Down syndrome. (2018, March 08). Retrieved September 30, 2018, from https://www.mayoclinic.org/diseases-conditions/down-syndrome/symptoms-causes/syc-20355977

What is Down Syndrome? | National Down Syndrome Society. (n.d.). Retrieved September 30, 2018, from https://www.ndss.org/about-down-syndrome/down-syndrome/

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