On the left there are parents who have Sickle Cell Anemia, in the middle the parents have Sickle Cell Trait and on the right the parents are normal. If you look at the figures on the left you note that a father who has Sickle Cell Anemia produces sperm that only carry the gene for sickle hemoglobin and the mother produces eggs that only carry the gene for sickle hemoglobin. When parents have the Sickle Cell Trait they can produce two types of sperm and two types of eggs; the father can produce sperm that carry the gene for sickle hemoglobin and sperm that carry the gene for normal hemoglobin and the mother can produce eggs that carry the gene for sickle hemoglobin or the gene for normal hemoglobin. Over on the right, the normal parents only produce sperm and eggs that carry the gene for normal hemoglobin.