Final answer:
Sickle-cell anemia is a genetic blood disorder where red blood cells take on a sickle or crescent shape, causing various issues. It is caused by the production of abnormal hemoglobin S.
Step-by-step explanation:
Sickle-cell anemia is a genetic blood disorder characterized by the production of an abnormal type of hemoglobin called hemoglobin S. This abnormal protein causes red blood cells to take on a sickle or crescent shape, especially in low oxygen concentrations. The sickle-shaped cells can block blood vessels, leading to a variety of serious problems such as pain, tissue damage, and organ dysfunction.