What does SS mean in sickle cell genetics?

• A. The person does not have sickle cell disease
• B. The person is a carrier of sickle cell disease
• C. The person has sickle cell disease
• D. The person shows symptoms only under stress

Answer: (A)

SS means two copies of the sickle cell allele, so the person has two HbS genes. This is an autosomal recessive situation, and having two HbS alleles causes sickle cell disease. The abnormal hemoglobin S causes red blood cells to sickle, leading to anemia and painful crises. So the statement that this person has sickle cell disease is the correct interpretation of SS. If someone had one normal allele and one HbS allele (AS), they would be a carrier with typically no disease symptoms. Saying symptoms only under stress doesn’t define the genotype; stress can trigger crises in someone who already has the disease, but the presence of disease is determined by having two HbS alleles.