HELP WITH BIOLOGY URGENT

Question

Sickle-cell anemia is an interesting genetic disease. Normal homozygous individials (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.

11% of an African population is born with a severe form of sickle-cell anemia (ss), 

What is the frequency of the recessive allele ?

What is the frequency of the dominant allele? 

What percentage of the population will be more resistant to malaria because they are heterozygous (Ss) for the sickle-cell gene?

please answer my three questions

 

Answer 1

This is all based on the Hardy-Weinberg equilibrium: p² + 2pq + q² = 1(100%) and where p+q=1. p² is frequency of homozygotes for "S" and q² is frequency of homozygotes for "s" and 2pq is frequency of heterozygotes.

The only way to answer this question would be if you were only interested in the frequency of alleles in the African American (AA) population. The frequency of "ss" carriers in the AA population is 11% as you mentioned. 11%=.11. The square root of .11 would be .33 or ~33% for the recessive allele "s". So our p=.33 because p² is .11 or 11%.

.33² is .11 or 11%. So we get back to the 11% of "ss" carriers in the AA population.

1-.33 would be the frequency of the dominant allele "S" which would be .66 or ~66%. In order to get the frequency of heterozygotes you would multiply s*S*2 or 2*p*q which would be .43 or 43%.

Please go ahead and give me a rating (good or bad) if I helped. Or feel free to ask a follow up question :)