2. 10-points: The MN blood group in humans is under the control of a pair of...

2. a) As 556 individuals are studied, total number of alleles will be (556 x 2) or 1112 (Because each individual will have 2 alleles).

Now, frequency of LM allele = Number of LM allele / Total number of alleles = (167 x 2 + 280) / 1112 = 614/1112 = 0.5522 (Up to 4 decimals)

So, frequency of LN allele = Number of LN allele / Total number of alleles = (109 x 2 + 280) / 1112 = 498/1112 = 0.4478 (Up to 4 decimals)

b) Under Hardy-Weinberg equilibrium-

Expected number of MM = (Frequency of LM allele)² x Total population = (0.5522)² x 556 = 169.54 170

Expected number of NN = (Frequency of LN allele)² x Total population = (0.4478)² x 556 = 111.49 111

Expected number of MN = 2 x Frequency of LM allele x Frequency of LN allele x Total population = 2 x 0.5522 x 0.4478 x 556 = 274.97 275

Now, = + + = 0.1799 (Up to 4 decimals)

Now, degrees of freedom = 1

From the distribution table we find that probability of = 0.1799 with degrees of freedom 1 falls between 0.1 & 0.9. As the probability is greater than 0.05, we can say that difference between observed & expected values are due to chance alone & no significant difference exist between them. So, the genotype frequencies fit to the Hardy-Weinberg distribution.