Question: how can you tell the difference between good genes and bad genes?

Lilian Hunt answered on 17 Mar 2014:

Genes themselves aren’t really good or bad, it’s the mutations in them that can make them good or bad. For example, people with cystic fibrosis have a mutation in a gene that causes problems with their mucus and can be life threatening. Everyone has that gene but only people with cystic fibrosis have two copies of the mutation that causes problems. Genes can get mutations in some cells sometimes that are very harmful. For example, in cancer, some of your cells can randomly get a mutation that causes them to divide lots and not die resulting in a tumour. The gene that will have mutated would be needed for every day life as your cells constantly need to divide, but the mutation will cause this to happen dangerously too much.

So there’s not really any bad genes, as we need our genes to be human, but there can be bad mutations in them that cause us problems!