Are genetic mutations always harmful?
Although humans are genetically 99.9% identical, we all have differences in our genes that make us unique. Most of these differences are not harmful and have little or no impact on our health (for instance, variations in genes that cause different eye colors). In some cases, a gene variation can cause a small increase or decrease in your chance to develop a disease. More rarely, a gene mutation causes a person to have a specific disease (like cystic fibrosis, Tay Sachs disease or sickle cell disease) or to have an increased chance of developing a specific condition (like breast cancer).
