Answer:
A DNA mutation causes sickle-cell anemia.
Step-by-step explanation:
Sickle cell anemia is caused by a single code letter change in the DNA. This in turn alters one of the amino acids in the hemoglobin protein. Valine sits in the position where glutamic acid should be. The valine makes the hemoglobin molecules stick together, forming long fibers that distort the shape of the red blood cells, and this brings on an attack.