What is a Punnett square used for?

• A. Measuring allele frequencies in a population.
• B. Predicting the genotypes and phenotypes of offspring from parental allele combinations.
• C. Determining DNA sequence alignment.
• D. Calculating metabolic rate.

Answer: (B)

Punnett squares help visualize how parental alleles can combine in offspring, allowing you to predict the genotypes and the resulting phenotypes for a trait that follows simple Mendelian inheritance. To use one, you write the gametes from one parent across the top and from the other parent down the side, then fill each box with the combination of alleles from the corresponding gametes. Each box represents a possible genotype for a child, and counting how many boxes show each genotype gives you the probabilities. If a dominant allele is present, you can infer the likely phenotype from the genotype. This tool is most straightforward for single-gene traits with clear dominant-recessive patterns; more complex inheritance patterns need different models. It isn’t used to measure allele frequencies in a population—that’s population genetics. It isn’t for determining DNA sequence alignments—that’s a bioinformatics task. It also isn’t about metabolic rate, which is a physiological concept.