Suppose that there are six pairs of alleles which control height and that every dominant allele adds 5cm to the stature. Assume also that the average height of an adult (with equal numbers of recessive and dominant alleles) is 160cm

   (a) What is (i) the tallest, (ii) the shortest person you would expect from this pattern?

   (b) On this basis, what would be the minimum difference in height among any two people?

   (c) Why is this minimum difference unlikely to be observed in reality?

a) In this model there are twelve alleles (six pairs) which could contribute to stature. An average person would be expected, therefore, to have six dominant and six recessive alleles.

 (i) The shortest person will therefore, lack the dominant alleles and be 30cm (6 x 5) shorter  than average, i.e. 130cm. (ii) The tallest person will have an additional six dominant alleles and therefore be 30 cm taller than average, i.e. 190cm.

b) If stature were controlled solely by genes, the minimum difference between individuals would be 5cm.

c) Since height is also influenced by nutrition and health, it is very unlikely that people would vary by exactly 5cm.