To  generate phenotypic ratios in the F[2], consider the A/a, B/b, and
   C/c  gene  pairs  separately.  For example, for the A/a pair, the F[1]
   cross is Aa x Aa.

   In the F[2], a phenotypic ratio of 3/4 A: 1/4 a, and a genotypic ratio
   (not  shown  here)  of  1/4  AA:1/2  Aa:1/4  aa  is produced, assuming
   independent assortment.

   The same ratios apply to the BB x bb and CC x cc crosses.

   The  proportions  of  organisms expressing each phenotypic combination
   can  be  predicted  by multiplying the individual probabilities, using
   the product law.