by Cory Maxwell ’24
Down Syndrome: Learn, Support, Give Back
Have you ever met anyone that has Down syndrome? Maybe you have a relative with it, or maybe a friend. We all interact with people who have disabilities, but have we ever stopped to think about what they actually are? In this article we will be asking four questions about Down syndrome: What is Down syndrome, what are the causes of Down syndrome, what effects does Down syndrome have on a person, and what is life like for someone with Down syndrome? Finally, why should we at Murphy care about Down syndrome?
What is Down Syndrome?
Down syndrome is a genetic disorder that occurs in babies when they have an extra copy of the twenty-first chromosome. That is why Down syndrome is also called Trisomy Twenty-One, which literally means three chromosome twenty-ones. It doesn’t especially occur in one group in particular, but children who are born from mothers over thirty-five are put at a higher risk. It is also possible for there to be three copies of another chromosome (eg. Edward’s syndrome occurs when there are three copies of chromosome eighteen).
What are the Causes of Down Syndrome?
There are three causes for Down syndrome: Nondisjunction, Robertsonian Translocation, and Mosaicism. Each of these processes causes a baby to have an extra copy of chromosome twenty-one. Let’s look at each one in detail.
- Nondisjunction
Nondisjunction is when a cell fails to split properly in meiosis (the process in which sex cells are split). This can also happen in mitosis (the process in which normal cells are split), but this is much rarer. In meiosis, a cell with forty-six chromosomes (two of each of the twenty three chromosomes) splits itself into two sex cells each containing twenty-threechromosomes (one of each chromosome). In some cases, the cell is split, but a pair of chromosomes is not. This results in one sex cell with two of the chromosomes that failed to split, and the other sex cell having no copies of that chromosome. About ninety-five percent of Down syndrome cases happen when one of the two sex cells within the baby has an extra copy of chromosome twenty-one due to nondisjunction.
- Robertsonian Translocation
Chromosomes have a long arm and a short arm. The long arm carries most of the important information, while the short one is generally unnecessary. In Robertsonian Translocation, the two arms of a chromosome are split and “translocated” onto another chromosome which has also split its arms, creating a hybrid chromosome. When such chromosomes go through meiosis, and a normal opposite sex cell is combined to it, there are six possible outcomes- one of them being Down syndrome. Though this happens, it is very rare, and only four percent of Down syndrome cases are caused by this.
- Mosaicism
The previous two causes of Down syndrome were mistakes in meiosis, but mosaicism occurs in a mitotic error, or a mistake in mitosis. This error happens in the womb as the developing baby grows. Nondisjunction happens at some point in the development of the baby, and the cell with an extra chromosome continues in the mitotic process, causing the baby to have both normal cells and cells with an extra chromosome. The earlier this error happens, there will be more cells with an extra chromosome, and the later it happens, there will be less cells with an extra chromosome. When this happens with the twenty-first chromosome, it is called Mosaic Trisomy Twenty-One. This is even rarer than Robertsonian Translocation, causing only one percent of Down syndrome cases.
What Effects Does Down Syndrome Have on a Person?
Down syndrome affects every part of the person who has it, though in cases of Mosaic Down syndrome it is less severe because only part of the genes are affected. People with Down syndrome have various mental health problems, and are to some extent intellectually disabled. Their physical features are also unique, and they are more prone to suffer from certain diseases. Let’s look at each of these in more detail.
Mental Health
People with Down syndrome are to some extent intellectually disabled. IQ scores of Down Syndrome patients may range from twenty to seventy. To put it in other words, Down Syndrome patients usually have the intelligence of an eight to nine year old. But intellectual disability is not the only mental health problem they have – most Down syndrome patients have sleeping problems and anxiety. Some younger children with the syndrome behave impulsively and are hyperactive. Some adults with the syndrome may develop depression and/or dementia.
Physical Features
Because of an over-expression of chromosome twenty-one, the appearance of someone with Down syndrome is unique from everyone else. Here is a quick overview of the distinct physical features that someone with Down syndrome may have:
- A flattened nose bridge and face.
- Little white spots on their irises called Brushfield Spots.
- Upper-slanting eyes.
- Epicanthal folds, or folds that cover the inner corner of their eye.
- Creases that go straight through their hands called a palmar crease.
- A wider gap between their first and second toes.
- Possibly a fissured tongue.
Physical Health
Since Down syndrome affects the whole body, it naturally follows that it affects most of the organs, too. Someone with Down syndrome is prone to many physical ailments including
- Blood Cancers (such as ALL and AMKL)
- Duodenal Atresia (a closed duodenum, which is the first part of the small intestine)
- Sterility (in men)
- Congenital Heart Diseases (a heart disease that someone has when they are born, such as Atrioventricular Septal Defect, where there are holes between the different chambers of the heart and the valves are faulty)
What is Life Like for Someone Who Has Down Syndrome?
Aside from the aforementioned effects of Down syndrome on one’s health, someone with Down syndrome can live a somewhat normal life. Often children with Down syndrome are given a more personalized education, and there are many therapy programs that work to help them both physically and mentally. Furthermore, adults with Down syndrome can have jobs, drive a car, and have a family just like a typical person can. For all Down syndrome patients, there are many charities and foundations that can support them and make sure they can live a happy life such as the NDSS and NADS. Life expectancy for someone with Down syndrome is about sixty years old.
You might be wondering, “Why is it important to know all the little details about Down Syndrome?” This article may contain many technical details that aren’t relevant for all, but it is important to understand how people with Down Syndrome are different so we can better live out the Murphy Way. There are summer service hour opportunities that involve working with adults and children with Down Syndrome, such as Camp Providence, Top Soccer, and the Special Olympics, and this is a great way to live out the Murphy Way and make your Service Hour load lighter for the next year.
Sources:
Cdc.gov Today’s Parent (on Youtube)
Into the Jungle 