The sickle shape makes it hard for the blood cells to get around in the blood vessels. Another disease that is inherited in this direct way is cystic fibrosis. This is a disease in which mucus clogs the lungs. Even chromosomes are invisible to the naked eye. When these paired chromosomes have been stained, however, they can be seen under a very good magnifying microscope.
Most diseases have a non-gene trigger.
That disease is PKU, in which protein is not eliminated but builds up. If protein foods are eaten, the brain will not fully develop. Our environment, our care in using chemical products, our personal habits, and our diet and exercise can be important.