#Newsround #iPlayer #downsyndrome #worlddownsyndromeday #downsyndromeawareness #explainer

Welcome to the official BBC Newsround YouTube channel. Subscribe here ➡️ ➡️ ➡️ https://bit.ly/3bYidJ3

For daily news bulletins visit BBC iPlayer ➡️ https://www.bbc.co.uk/iplayer/episode...

People across the globe will be marking World Down Syndrome Day today.

The awareness day was first celebrated in 2006, and has been officially observed by the United Nations since 2012.

It is a day to raise awareness of the genetic condition. This year, the theme of World Down Syndrome Day is: With Us Not For Us.

The theme aims to discourage people from pitying those with Down's Syndrome, and instead to work together with them to create a more equal society.

One of the ways people mark the day is by wearing colourful socks - so if you see somebody out today in colourful socks, this might be why.

Read on to find out more about the condition...

Down's syndrome is a genetic condition which typically affects someone's learning and physical features.

It is not a disease, an illness or a condition that someone can catch.

How does Down's syndrome affect a person?

People who have Down's syndrome have different personalities and abilities to each other, just like anybody else.

Typically, everybody with the condition will experience some level of difficulty learning, so it might take a person with the condition a little longer to process information, carry out a task or learn new skills.

People may also share common physical characteristics (for example, a smaller mouth and one individual line across the palm of their hand), but they will look like their parents just like anybody else.

Individuals with Down's syndrome may be more likely to have some health problems - for example, with their hearing - so children with the condition might go to the doctor a little more often to keep on eye on their health. It can also cause speech problems, so a person might have speech therapy to help with this.

The majority of people with the condition walk and talk, go to ordinary schools, play sport if they wish and lead a fairly typical life.

The Down's Syndrome Association explains: "The level of support that a person with Down's syndrome needs as they grow older will be different from person to person."

How common is Down's syndrome?

About one in every 1,000 babies is born with the condition. There are currently about 60,000 people in the UK with Down's syndrome.

It is a little more likely for a woman to have a child with Down's syndrome if she has a baby when she is older.

It occurs completely by chance in all races, in all countries across the world.

What causes Down's syndrome?

Down's syndrome is a genetic condition, which means it is caused by something in a person's genes.

Our bodies are made up of billions of tiny cells, and each cells contains genes. Genes are grouped together in structures called chromosomes.

Genes contain important information that determine features like our eye colour and whether we are a boy or a girl.

Usually, cells contain 46 chromosomes. But Down's syndrome happens when all or some of the cells in a person's body has 47 chromosomes due to an extra copy of chromosome 21. This is why you might also hear the condition being called trisomy 21.

Professor Jerome Lejeune proved that this is what causes Down's syndrome in 1959.

There are three types of Down's syndrome:

• Trisomy 21 - All the cells have an extra chromosome 21 (most people with Down's syndrome have this type)

• Translocation - The added genetic material on chromosome 21 is attached to another (around 4% have this type)

• Mosaic - Some cells in the body, not all, have an extra chromosome 21 (this is the least common type)

Down's syndrome is named after Doctor John Langdon Down who first published information about the condition in 1866.

Since then, we've learned a lot more about the condition

Thumbnail photo from Getty Images.

Please visit www.bbc.co.uk/newsround/13865002 for tips about what to do if you are feeling sad about what you've seen, heard or read.

We have everything for an inquisitive mind – do you want to know what’s going on in the world? Complex stories explained in a way that makes sense to you? Well, you’re in the right place!