What does a Punnett Square primarily illustrate?

A Punnett Square is a valuable tool used in genetics to predict the possible genetic combinations of offspring from parental genotypes. It visually represents the alleles contributed by each parent, allowing one to determine the probabilities of inheriting particular traits. By organizing the alleles in a grid, it becomes easy to see all potential combinations and their corresponding probabilities, hence illustrating the possible traits of the offspring that could result from a specific cross.

The other options do not accurately capture the primary purpose of a Punnett Square. While gene mutations involve changes in the DNA sequence, and chromosomal structures pertain to the organization of chromosomes within cells, neither of these concepts is the focus of a Punnett Square. Environmental influences on genes, though important in the broader context of phenotypic expression, are not represented within the scope of a Punnett Square, which strictly deals with inherited traits passed down from parents based on their genetic make-up.