A gene mutation can affect the cell in many ways. Some mutations stop a protein from being made
at all. Others may change the protein that is made so that it no longer works the way it should or it may not even work at all. Some mutations may cause a gene to be turned on, and make more of the
protein than usual. Some mutations don't have a noticeable effect, but others may lead to a disease.For example, a certain mutation in the gene for hemoglobin causes the disease sickle cell anemia.