An individual with a phenotype of HbSS exhibits sickle cell disease. An individual with a phenotype of HbAS allele carries the sickle cell trait. An individual with a phenotype of HbAA does not possess sickle cell disease and does not carry the trait. The Punnett square demonstrates the resulting progeny after a cross between the two individuals of the genotype HbAS, who are carrying the sickle cell gene. The probability of getting sickle cell disease in the offspring comes out to be 25 percent.
