Q. 96 In a population, 600 individuals have MM blood group, 300 have MN blood group and 100 have NN
blood group. What will be the frequencies of M and N alleles in this population?
(A) M 0.75 and N 0.25
(B) M 0.65 and N 0.35
(C) M 0.85 and N 0.15
(D) M 0.55 and N 0.45
Problem Data
Total individuals: 600 MM + 300 MN + 100 NN = 1000
- Each MM contributes 2 M alleles (1200 M alleles)
- Each NN contributes 2 N alleles (200 N alleles)
- Each MN contributes 1 M and 1 N allele (300 M + 300 N alleles)
- Total alleles: 2000
Correct Calculation
Frequency of M allele (p) = (1200 + 300) / 2000 = 1500 / 2000 = 0.75
Frequency of N allele (q) = (200 + 300) / 2000 = 500 / 2000 = 0.25
p + q = 1.0, confirming the result
Option Analysis
(A) M 0.75 and N 0.25: Matches exact calculation above.
(B) M 0.65 and N 0.35: Likely from mistaking MN frequency (0.3) as q² or ignoring total alleles.
(C) M 0.85 and N 0.15: Possible if only MM proportion (0.6) doubled incorrectly to 1.2, then adjusted.
(D) M 0.55 and N 0.45: Could arise from averaging phenotypes (e.g., 0.6 MM + 0.15 from half MN).
