You might have more than one person in your family who has HD. This is because HD runs in families – it is hereditary. This means it can be passed from parents to their children. People might say that you look like other people in your family – this is because of your genes. Genes are passed to you from your parents – that’s why you might have freckles like your dad, or brown eyes like your mum. You have about 30,000 different genes in your body.

Genes are sections of DNA carried on your chromosomes. These genes are all different, and are programmed with different information. They decide things like the colour of your hair and your eyes, how tall you are, etc. They are like a recipe book - your genes are the ingredients that make you uniquely you. Everyone has a different recipe - that’s why we’re all different shapes and sizes. Most cells in your body have 23 pairs of chromosomes. Each parent gives you 1 chromosome in each pair. Our genes are strung out along our chromosomes and there are 100s of genes in each chromosome. We have 2 copies of each gene as well – one from each parent.

People can be identified because of the differences in their genes and the DNA that makes them. DNA can be extracted from one cell of our body, such as a single skin or blood cell, or even a hair root. That’s why on your fave crime dramas, they search the crime scene for DNA evidence. People can then be identified by their DNA.

For more info on genes and genetics, check out www.kidshealth.org.

Sometimes genes don’t work properly. In people with HD, a faulty gene causes things to go wrong in the brain. If a parent has HD, they have 1 faulty copy of the gene and 1 good copy. They may pass either of these on to their children. Their children therefore have a 1 in 2, or 50% chance of inheriting the faulty gene. You may hear people saying you are “at risk” – this just means you have a 50% chance of inheriting the faulty gene. If your grandparent has HD that means your parent is at risk. If they do not have the faulty gene, then you are no longer at risk.

The specific gene that causes HD was identified in 1993. It is located on chromosome 4. No-one knows exactly how this faulty gene causes HD and there is a lot of research going on all over the world to try and find out. Somehow having the faulty gene causes the build up of a protein (a type of body chemical) called Huntingtin in some of the brain cells which makes them deteriorate and die. Once we know how this works, we can try and find a way to stop it happening or at least slow it down. We know a lot more about the HD gene now than ever before and different medications and approaches are being tested, so the future looks positive!

For more info on the latest research, check out www.hdlighthouse.org or heaps of other links on our More Links and Reading page.