A Punnett square is used to predict...

• A. DNA replication accuracy.
• B. Mutation rates.
• C. Chromosome structure.
• D. Possible genetic outcomes (genotypes and phenotypes) of a cross.

Answer: (D)

Punnett squares show all the possible allele combinations that offspring can inherit from their parents, so they predict the genotypes and, depending on dominance, the phenotypes that could result from a cross. By pairing the alleles each parent can pass with those from the other parent, you can see the probabilities of different genotype outcomes and translate those into corresponding phenotypes when one allele hides the other or when both alleles have an effect. This tool is about forecasting genetic outcomes of matings, not about how accurately DNA is copied during replication, how often mutations occur, or the physical structure of chromosomes. So the most accurate use of a Punnett square is to forecast possible genetic outcomes (genotypes and phenotypes) of a cross.