<prompt> Sickle cell trait patient do not have manifestations as that of Sickle cell disease, because?50 HbS is required for occurrence of sicklingHbA prevents sickling50 sicklesHbA prevents polymerazitation of Hbs  <response>: Ans. is a i.e., 50 Hbs is required for occurence of sickling Sickle cell disease occurs in following forms 1. Heterozygous state, i.e., sickle cell trait. 2. Homozygous state, i.e., sickle cell anemia. o The most impoant factor for sickling is the amount of HbS in the cell. o In sickle cell trait heterozygous state, only about 40 of the hemoglobin is HbS, this is insufficient to produce sickling manifestations. o In homozygous state, almost all the hemoglobin in the red cell is HbS, therefore they undergo sickling. 