each parent carries one sickle cell allele & sickle cell anemia is a recessive trait in human ->  each parent has one dominant gene and a recessive gene for sickle cell anemia  each parent has one dominant gene and a recessive gene for sickle cell anemia & heterozygous dominant organisms have one dominant gene and one recessive gene ->  both parents are heterozygous dominant for sickle cell anemia  both parents are heterozygous dominant for sickle cell anemia & if a heterozygous dominant organism is crossed with a heterozygous dominant organism , then the offspring will have a 25% probability of being homozygous recessive ->  the offspring of heterozygous dominant parents will have 25% probability of being homozygous recessive for sickle cell anemia  the offspring of heterozygous dominant parents will have 25% probability of being homozygous recessive for sickle cell anemia & homozygous recessive organisms will show the recessive trait ->  the offspring of heterozygous dominant parents will have 25% probability of having sickle cell anemia  the offspring of heterozygous dominant parents will have 25% probability of having sickle cell anemia & one in four is the same as 25% -> one in four of the offspring of heterozygous dominant parents will have sickle cell anemia