In a monohybrid cross, such as the one in Figure below, the Punnett square shows every possible combination when combining one maternal (mother) allele with one paternal (father) allele. In this example, both organisms are heterozygous for flower color Bb (purple). Both plants produce gametes that contain both the B and b alleles. The probability of any single offspring showing the dominant trait is 3:1, or 75%. To develop a Punnett square, possible combinations of alleles in a gamete are placed on the top and left side of a square. For a monohybrid cross (Table below), individual alleles are used, whereas for a dihybrid cross (Table below), pairs of alleles are used. A Punnett square for a monohybrid cross is divided into four squares, whereas a Punnett square for a dihybrid cross is divided into 16 squares. How many boxes would a Punnett square need if three traits were examined? The squares are filled in with the possible combinations of alleles formed when gametes combine, such as in a zygote.