What is Down Syndrome?
Down syndrome is something a person is born with, it’s not an illness or something you can catch. It happens when a baby is born with an extra copy of one chromosome, called chromosome 21.
Every person has tiny structures in their cells called chromosomes, which carry all the instructions that make us who we are — like how tall we might be, our hair colour, or how our body grows. Most people have 46 chromosomes (23 pairs), but people with Down syndrome have 47 because of that extra copy of chromosome 21.
That extra chromosome changes the way their body and brain develop, which can cause some differences in learning and physical features. But everyone with Down syndrome is unique — they have their own personality, talents, and interests, just like anyone else.
Myths & Facts about Down Syndrome
Myth: People with Down syndrome are always happy.
Truth: People with Down syndrome experience a full range of emotions, just like everyone else.
Myth: People with Down syndrome can’t read or write.
Truth: Children and adults with Down syndrome may have cognitive and mobility delays at different levels, but with the right support, they can achieve their goals at their own pace.
Myth: People with Down syndrome cannot have relationships, get married, or have a job.
Truth: People with Down syndrome can lead happy, fulfilling lives, forming meaningful relationships, working, and contributing to the community.
How common is Down syndrome?
Down syndrome is actually the most common chromosomal condition in the world.
In the United States, about 1 in every 775 babies is born with Down syndrome — that’s roughly 5,000 babies each year.
In the UK, the numbers are pretty similar. Around 1 in every 1,000 babies is born with Down syndrome, although some reports show it can be as frequent as 1 in every 850 births.
Here in Guernsey, there isn’t official data, but the local Down Syndrome Group supports around 14 families on the island — showing that even in a small community, lots of people are connected by shared experiences and support.
Are there different types of Down syndrome?
Yes there are 3 types of Down Syndrome
Trisomy 21 (Nondisjunction)
Most people with Down syndrome — about 95% — have this type. It happens by chance when cells are dividing to make a baby. Normally, each cell should get two copies of every chromosome, but sometimes, the 21st pair doesn’t split properly. This leaves the embryo with three copies of chromosome 21 instead of two. As the baby grows, that extra copy is copied into every cell, which causes the features linked to Down syndrome.
2. Mosaicism
This is a rare type, only about 2% of cases. It means the person has a mix of two kinds of cells:
- Some with the usual 46 chromosomes
- Some with 47 chromosomes, including the extra chromosome 21
Because of this mix, people with mosaic Down syndrome might show fewer signs of Down syndrome, but everyone is different — abilities and traits vary a lot from person to person.
3. Translocation
This type happens in about 3% of cases. Here, the person still has 46 chromosomes total, but one of the chromosomes — usually number 14 — has an extra piece of chromosome 21 stuck to it. That extra part causes the same effects as having an extra full chromosome 21.