When calculating a genotypic ratio, it is common to use the Punnett Square. The square takes the two alleles from each parent and gives a ratio depending on their dominant or recessive genes. Most Punnett Squares contain four squares that give a diverse ratio of what genes may occur. If R is dominant, and r is recessive, then when divided, the genotypes would be: RR, Rr, Rr, and rr. 75% will be dominant and 25% will be recessive.