What actually is Down Syndrome???

Disclaimer: I am no scientist.

I really wish I was good at science, and at college I particularly found Human Biology interesting... but it wasn't a natural strength haha!

With that being said, I shall try and explain to the best of my (very limited!) ability what Down Syndrome actually is.

The main thing to know about DS, is that it is a chromosomal difference and that there are three different types:

T21 (Trisomy 21) is the name given to the most common type of Down Syndrome where the individual has an extra copy of chromosome 21. Typically, you would have 2x copies of chromosome 21, whereas an individual with DS has 3x copies of chromosome 21. This is across all their DNA and cells, and the extra copy changes the instructions on how the baby’s body and brain should develop. Often, chromosomal differences (such as deletion or other trisomies - where there are 3x a chromosome) can have unknown and potentially severe consequences… but Down Syndrome is common and relatively well researched. T21 is the type of DS Oriana has.

You can also get Translocation Down Syndrome where the extra copy of chromosome 21 attaches to another chromosome. This is far more rare than T21, and can be hereditary (a parent can be a carrier but not have DS themselves).

Finally, there is Mosaic Down Syndrome (the rarest type) where some of the cells will have an extra copy of chromosome 21, but some won’t (unlike T21 where they all do). The amount of cells with the extra copy of the chromosome in varies between each individual with Mosaic DS. Whilst you may think of Mosaicism as being 'partial' DS, it is still DS and the individual can have as many physical markers of someone with T21, and/or similar IQ and learning abilities. Some individuals however, do not have as many physical markers and/or have slightly higher IQ than someone with T21 - it all depends on how the extra 21st chromosomes interact with the rest of the biology of the individual.

So, there is my attempt at a quick DS summary! I hope that gives you an overview of what DS is, and I can only apologise that my science isn't more thorough! If you are a little bit nosy like me, it may interest you to type 'trisomy 21 karyotype' into a search engine (under the image search) and it will show you what the chromosomes look like in a person with DS. How amazing is the human body?!

(If you want any more depth on any of the above, I suggest you research that yourself because I am worried I will start tripping up and my poor grasp of Human Biology will be apparent!)