The type of Down syndrome that Jackson has is Trisomy 21, and this is the name I actually prefer using. This name refers to the chromosomal makeup of people with this diagnosis. Humans typically have 46 chromosomes. A person with Down syndrome has 47 chromosomes. More specifically, they have an extra, or third, copy of the 21st chromosome-thus the name Trisomy 21.
There are also three types of Down Syndrome: Trisomy 21, Translocation, and Mosaicism. Trisomy 21 is the most common form of Down syndrome with 95% of people who have DS having this type. Someone with this diagnosis has 47 chromosomes in every cell in their body.
A person with Translocation Down syndrome still technically has 46 chromosomes, but either a full or partial extra copy of the 21st chromosome attaches itself to another chromosome and causes this person to have the characteristics of Down syndrome. Translocation is found in about 4% of people with DS, and this is the only form of DS can be genetically passed down, or hereditary.
Mosaicism is the rarest type of DS; only about 1% of the population of people with DS has this diagnosis. A person with Mosaicism has a mixture of cells that have 46 and 47 chromosomes. The cells with 47 chromosomes have an extra copy of the 21st chromosome.
This brings me to the misconception that there are different "levels" of Down syndrome. Just as there is no way to know what a typical child, one with 46 chromosomes, will accomplish, there is no way to determine whether a person with Down syndrome, regardless of type, will be "high" or "low" functioning. There is no set spectrum that doctors use to diagnose what children with DS will achieve in their lives. There is no such thing as having "just a touch" or a "slight case" of DS. There are many characteristics a person with DS can have, but these characteristics will express themselves differently in each individual. While some of the physical characteristics of DS are the most easily recognizable, people with DS still resemble the members of their family more than anyone else.
Jackson's extra chromosome is just one small part of him. Most days we don't even think about it, but it is pretty cool to think about how rare his genetic code actually is. We like to think of him as "chromosomally enhanced"! Below you can see a beautiful picture of genome of someone with Trisomy 21.
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