STPM Biology - chapter 18: Revision essay question 3

3. In a given population, only the "A" and "B" alleles are present in the ABO system.  There are no individuals with type "O" blood or with O alleles in this particular population. If 200 people have type A blood, 75 have type AB blood, and 25 have type B blood, what are the alleleic frequencies of this population (i.e., what are p and q)?


Answer


         Type A blood = homozygous AA = 200
         Type B blood = homozygous BB = 25
         Type AB blood = heterozygous AB = 75

       The frequency of A = 2 (200) + 75 
                                              2 (300)
                                        = 0.792
                                        = p
        Since p + q = 1,
        then q = 1 – p
                    = 1 – 0.792
                    = 0.208



Assignment submitted by L.Y., Kong,  S. H., Lim, S. C., Soo, C. W.