Individuals who are homozygous (with two copies of the abnormal hemoglobin beta allele) have sickle-cell anaemia, while those who are heterozygous (with one abnormal allele and one normal allele) experience resistance to malaria without severe anemia.
Individu yang homozigot (dengan dua salinan dari alel hemoglobin beta abnormal) memiliki anemia sel sabit, sementara mereka yang heterozigot (dengan satu alel abnormal dan satu alel normal) memiliki resistensi terhadap malaria tanpa anemia berat.