What is a Punnett square used for?

A Punnett square is a visual tool used in genetics to predict the possible genotype and phenotype combinations that can result from the mating of two parents. By aligning the alleles of each parent along the top and side of a grid, the Punnett square allows for an organized way to determine the probabilities of inheriting particular traits. This is especially useful in studying inheritance patterns associated with simple Mendelian traits, where single genes affect certain characteristics.

The framework of a Punnett square provides a direct representation of how alleles combine during fertilization, enabling individuals to explore the genetic outcomes resulting from specific parental gene combinations. This is fundamental in the study of Mendelian genetics, where understanding the inheritance patterns of dominant and recessive traits is crucial.

In contrast, while the other options involve important concepts in biology, they do not directly relate to the primary function of a Punnett square. For instance, modeling genetic mutations implies a focus on alterations in DNA sequences rather than typical inheritance patterns, while identifying cellular respiration stages and measuring gene expression levels pertain to processes and metrics in cell biology rather than genetic probability. Thus, the correct answer highlights the specific usage of the Punnett square in predicting genetic combinations.