What is the primary purpose of a Punnett square?

The primary purpose of a Punnett square is to predict outcomes of genetic crosses. This tool helps to visualize the different combinations of alleles that offspring might inherit from their parents based on their genotypes. By organizing the parental genotypes in a grid format, it shows all possible allele combinations in the gametes and allows one to calculate the probabilities of each potential genotype or phenotype in the offspring.

While illustrating genetic traits and displaying dominant and recessive traits are important functions of the Punnett square, they are auxiliary to its main use in predicting genetic outcomes. Mapping out evolutionary relationships is unrelated to the function of a Punnett square, as that concerns phylogenetics rather than inheritance patterns. Thus, predicting the outcomes of genetic crosses is the core function that makes the Punnett square a valuable tool in genetics.