Hello there. My name is Daniel Green at the Titan Biology Institute. Beside me is Swiss scientist Friedich Miescher and Felix the double helix of DNA (Deoxyribonucleic acid)
Here are Valance and Rubi. They are siblings who share similarities, but also differences. See, their parents look like both of their children but the parents's features are inherited from their parents and so on.
DNA is taken from both sides of your family. You can have your mother's eyes but have your dad's tone of skin. This is what we call variation, and it's why humans don't look similar unless they're related.
But sometimes your DNA is changed and you end up looking completely different from your siblings or parents. This is what is known as a MUTATION.
Mutations vary, from the simple such as blonde hair from your grandad to being an albino or having no hair at all. Mutations such as Autism are purely genetic and have nothing to do with outside factors.
However, birth defects can be caused by outside factors, such as smoking and drinking. Others can be genetic and most of the time they are. This was Inheritance and DNA brought to you by Daniel Green!