Sickle Cell Disease Is Recessive
To get sickle cell disease, people need two copies of the sickle hemoglobin (HbS) allele—they must be homozygous.
That means the disease is recessive.
People with one HbS allele and one normal (HbA) allele are heterozygous.
They don’t have sickle cell anemia.
The Inheritance of Sickle Cell Disease
People with 2 sickle cell alleles are homozygous with sickle cell disease. People with 1 sickle cell allele are heterozygous with sickle cell trait.