Sickle cell anemia is a genetic condition that affects the synthesis of hemoglobin

Sickle cell anemia is a genetic condition that affects the synthesis of hemoglobin molecules in humans. There is an allele for normal hemoglobin (HB ) and an allele for sickle cell hemoglobin (Hb ). Neither of the two alleles (HB or Hb)) can completely hide the presence of the other. Which of the following best describes the alleles for sickle cell anemia?