This lesson predicts genetic probability using monohybrid and dihybrid Punnett Squares. In 1905, Reginald Punnett, devised a short-hand way of determining the expected proportions of possible genotypes in the offspring of a cross. This method is called the Punnett Square. It takes account of the fact that fertilization occurs at random, as Mendel's Law of segregation states. If the genotypes of the parents are know a Punnett Square can be used to predict the possible genotypes of offspring.