Our cells divide to make copies of themselves, so our bodies can grow. When those copies are made, all the genes inside the cell are copied as well. The DNA copying process isn’t perfect – it is such a big job that random errors, called genetic variants, can occur like a typo. Our body has ways of fixing these errors, but occasionally one isn’t caught and stays there. 

When that happens, the new cell has a permanent genetic variant, which gets copied into new cells when that cell divides, and so on. These genetic variants usually cause us no harm whatsoever. Every once in a while, a particular genetic variant actually prevents a gene from performing its usual function. These harmful errors are called pathogenic variants, sometimes referred to as mutations.