October 3 – Three Types of Down Syndrome!

When I say Coldon has Down syndrome, did you wonder what type of Down syndrome he has? Wait… there’s more than one? 

Actually yes, there are three; nondisjunction, translocation and mosacism. Coldon was diagnosed with non-disjunction Trisomy 21. (there are several different “nicknames” out there. Our genetics counselor called it “Free Trisomy 21.”) I know you’re next question is, “what hat does that mean?

Well… our genes are the blueprint of our bodies and mind. They determine the way we look, how we think, how we act; even the way we smell. According to the U.S. National Institutes of Health (NIH), “chromosome 21 represents 1.5 to 2 percent of the total DNA in cells.” I can’t even wrap my head around the number of cells in our bodies and how much of our genetic material is impacted by having a third 21st Chromosome. (Genetics peeps, feel free to enlighten us!)

So, after the short genetics lesson, here you go…
Nondisjunction Trisomy 21 means there is a third copy of the 21st chromosome in 100% of the individuals genes. This is the most common form; approximately 95% of people who have Down syndrome have nondisjunction. 
Translocation means there is a third copy of the 21st chromosome, but all or part of it is attached to another chromosome. This is the only form of DS that is hereditary (the others are random) and it affects around 4% of individuals who have Down’s syndrome. 
Mosaicism (Mosaic) means there is still an extra 21st chromosome, but it isn’t present in every cell. This is the most rare form; with around 1% of the DS population. Because it isn’t located in every cell, many individuals who have mosaic DS may not have all of the characteristics and challenges as individuals with nondisjunction.

Now you know there is more to Coldon’s diagnosis than just Down syndrome. The genetics aspect of DS fascinated me, but it is incredibly complex. Keep in mind when thinking about Down syndrome, each individual is their own individual; they don’t fit the stereotypes for Down syndrome, because we are all different— all the individuals don’t even have the same extra 21st chromosome. How can we define our children as Down syndrome when each individual is genetically unique?

***I have ZERO medical background and Genetics, while it fascinates me, gives me a headache when I try to rap the information around my brain. So, I’ll explain best I can but you can visit these sites to learn more! National Down Syndrome Society (NDSS), Global Down Syndrome Foundation, National Down Syndrome Congress (NDSC) and National Institutes of Health (NIH)

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