Sickle cell disease is usually found among people of largely African or Mediterranean descent, for instance, whereas cystic fibrosis is far more common among those of European ancestry.

• 例如在美国，镰状红血球的病例主要在非洲裔、地中海裔族群中出现，而罹患囊肿性纤维化疾病的人，在欧洲裔族群中最常见。