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

Question

Sickle-cell anemia 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. Assuming an African-American child were born each day of the year, statistically, one of these children per year would have a severe form of sickle-cell anemia (ss). Assuming Hardy-Weinberg equilibrium of these alleles, what is the percentage of the African-American population that are sickle-cell carriers? (Note that these carriers will turn out to be more resistant to malaria, should they decide to visit a malaria-infested part of the world; sometimes there are bizarre perks to being a carrier of a horrible disease!). Enter a percentage number (round up to whole number) without percent sign (%)

Explanation / Answer

A year contains 365 days. Per year there are 365 African-American children born. OF these, 365 Children, on e child per year suffers from sickle cell. One in every 365 children suffers from sickle cell anemia.

The frequency of the recessive sickle cell (ss) African-American population= q2= 1/365=0.0027

Hence, q= frequency of s allele= square root of 0.027= 0.052= 5.2%

Frequency of S allele= 1-0.052= 0.948= 94.8%

The Hardy Weinberg equation is given as:

p2+2pq+q2=1

p2 = frequency of the homozygous genotype SS, q2 = the frequency of the homozygous genotype ss, and 2pq = frequency of the heterozygous genotype Ss.

Frequency of the heterozygous Ss individual that are carriers for sickle cell anemia= 2pq=2*0.948*0.052=0.0986

Percentage of sickle cell carrier in the African American Population = 0.0986*100=9.86%= Approximately 10%.

The number to be entered is 10

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