<Ul> <Li> Infected erythrocytes (red blood cells) tend to have lower oxygen tension, because it is significantly reduced by the parasite . This causes sickling of that particular erythrocyte, signalling the phagocytes to get rid of the cell and hence the parasite within . </Li> <Li> Since the sickling of parasite - infected cells is higher, these selectively get removed by the reticulo - endothelial system, thus sparing the normal erythrocytes . </Li> <Li> Excessive vacuole formation occurs in those parasites infecting sickle cells . </Li> <Li> Sickle trait erythrocytes produce higher levels of the superoxide anion and hydrogen peroxide than normal erythrocytes do, both are toxic to malarial parasites . </Li> </Ul> <Li> Infected erythrocytes (red blood cells) tend to have lower oxygen tension, because it is significantly reduced by the parasite . This causes sickling of that particular erythrocyte, signalling the phagocytes to get rid of the cell and hence the parasite within . </Li> <Li> Since the sickling of parasite - infected cells is higher, these selectively get removed by the reticulo - endothelial system, thus sparing the normal erythrocytes . </Li> <Li> Excessive vacuole formation occurs in those parasites infecting sickle cells . </Li>

Which of the following is true about the alleles for hemoglobin in humans