Explanation

Genes are information passed on by your Mum and Dad, and carried by your DNA on your chromosomes. There are over 30,000 genes on each chromosome, so many that we cannot see them all.

Genes decide everything about you and how your body works - what colour your hair is, how the muscles move when you smile, what your voice is like, even how your heart beats. So, if you have a genetic problem, it might be because certain genes don't work properly.