Punnett square
A Punnett square is a visual representation of a cross. The genotypes of the parents are denoted along the top and the side of the grid. The possible genotypes of the offspring are obtained by combining the different alleles in the grid.
The Punnett square below shows an example of a cross between a heterozygous father and a homozygous dominant mother.
Figure 1: Punnett square.