Sickle-cell anemia is an interesting genetic disease. Normalhomozygous individuals (SS) have normal blood cells that are easilyinfected with the malarial parasite. Thus, many of theseindividuals become very ill from the parasite and many die.Individuals homozygous for the sickle-cell trait (ss) have redblood cells that readily collapse when deoxygenated. Althoughmalaria cannot grow in these red blood cells, individuals often diebecause of the genetic defect. However, individuals with theheterozygous condition (Ss) have some sickling of red blood cells,but generally not enough to cause mortality. In addition, malariacannot survive well within these \"partially defective\" red bloodcells. Fitness of different genotypes is as follows: 50% of the SSindividuals survive and reproduce; 100% of the Ss individualssurvive and reproduce while only 5% of the ss individuals surviveand reproduce. Thus, heterozygotes tend to survive better thaneither of the homozygous conditions. If 9% of an African populationis born with a severe form of sickle-cell anemia (ss), whatpercentage of the population will be more resistant to malaria inthe second generation because they are heterozygous (Ss) for thesickle-cell gene?
Please note it is asking for the second generation! not thefirst!!!!
