Question

5. Sickle-cell disease is an interesting genetic disease. Normal homozygous individuals (SS) have normal blood cells that are easily infected with the malarial parasite. Thus, many of these individuals become very ill from the parasite and many die. Individuals homozygous for the sickle-cell trait (ss) have red blood cells that readily collapse when deoxygenated. Although malaria cannot grow in these red blood cells, individuals often die because of the genetic defect. However, individuals with the heterozygous condition (Ss) have some sickling of red blood cells, but generally not enough to cause mortality. In addition, malaria cannot survive well within these "partially defective" red blood cells. Thus, heterozygotes tend to survive better than either of the homozygous conditions. About 9% of the African population is born with the severe form of sickle-cell disease. a. What is the frequency of the S allele in the population? b. What percentage of the population will be more resistant to malaria because they are heterozygous (Ss) for the sickle-cell gene?

Answer 1

a. Frequency of S allele = 0.7

b. 42% of the population is resistant to malaria because they are heterozygous (Ss) for the sickle - cell gene.

About g% of the African population is boon with the severe from of sickle-cell disease. SS g% and P+9 = 1 Hardy-Weinberg principle; p? +229 + 92= ! Frequency of dominant allele Frequency recessire allele p2 = Percentage of home zygous dominant i nodiri duals. q? = Percentage of homozygous recessive individuals. 289 = Percentage of heterozygous individuals 9 = of 11 o og Here, 92 = 9 % q = Voog : 0:3 - 0.3 0.7 P = 1 - 9 = = 0.42 on 42% 2 x 0.780.3 209 =