Puzzle

... “Spock, how is your research into the physiology of the inhabitants of Rigel 4 going?” inquired Captain James T. Kirk of the USS Enterprise. “Fascinating, Captain,” replied his first officer. “Explain, Spock.” “Well, Captain, as you know, humans’ eye colour on Earth is determined by a single gene pair. Individuals with genotype bb have blue eyes and individuals with genotype BB or Bb have brown eyes.” “And you think that on Rigel 4 that is not the case?” asked Kirk. “I have some evidence that eye colour is determined by two gene-pairs. The genes being Bb in one gene pair and Ii in the other. An offspring receives at random one gene of each gene-pair from each of the parents. Those of genotype bb have no brown pigment at all. The presence of gene B ensures that brown pigment is present. The presence of gene I prevents the brown pigment from showing in the eyes even if it is present. Those of genotype ii show the brown pigment in their eyes if it is present in the individual.”*