Answer
Genes
Explanation:
Though heredity (passing of traits from parents to offspring), genes control various physical traits -- eye and hair color, amount of melanin in your skin, the shape of your nose or chin and others traits. There are also genes that, if present, can cause the development of a genetic disease (sickle cell, downs syndrome, Tay Sachs, and others). Scientists have also learned that there are other potential health consequences of genes. For example, they have discovered a breast cancer gene. This means that if the gene is present, there is a greater propensity for the development of the disease.
