Question

For the MN-blood group system, the frequencies of M and N alleles are 0.7 and 0.3, respectively. The expected frequency of MN-blood group bearing
organisms is likely to be
A. $42\%$
B. $49\%$
C. $9\%$
D. $58\%$

Answer 1

The MNS blood group system is a system where the human blood is recognized based on the presence of M, N, S, and s antigens on the surfaces of red blood cells. This system was first discovered in 1927. This mechanism has many distinct phenotypes and people who study genetic and anthropological research in the human population, give interest to this system.

Complete answer:
The MNS blood group system has more than 40 antigens. Two strongly polymorphic genes, known as GYPA (glycophorin A) and GYPB (glycophorin B), encode these antigens. The system consists of two pairs of codominant alleles, the M and N and the other is S and s. Alleles M and N are usually distributed at relatively equal frequencies in the population. The S and s alleles, though, have differing concentrations, the S allele appears in about 55 percent of whites and 30 percent of blacks, while the s allele appears in about 90 percent of people in both populations.
According to the Hardy–Weinberg principle, if the allele frequencies in a population with two alleles at a locus are $p$ and$q$, then the expected genotype frequencies are ${p^2}$,$2pq$, and ${q^2}$
At Hardy–Weinberg equilibrium, ${\left( {p + q} \right)^2} = {p^2} + 2pq + {q^2} = 1$
The frequency of MN $= 2pq = {{ }}2{{ }} \times {{ }}0.7{{ }} \times {{ }}0.3$
The expected frequency of MN group $= \left( {2{{ }} \times {{ }}0.7{{ }} \times {{ }}0.3} \right) \times 100 = 42\%$
So, the correct answer is option A that is $42\%$.

Note: The Hardy-Weinberg theory , also known as the Hardy-Weinberg equilibrium, states that, in population genetics the allele and genotype frequencies in a population will remain stable from generation to generation, in the absence of other evolutionary factors.