In a Punnett square, what do the letters on the top and side represent?

In a Punnett square, the letters on the top and side represent the alleles contributed by each parent. Each parent has two alleles for a trait (one inherited from each of their own parents), and these alleles are expressed as letters to demonstrate the possible combinations that can result in the offspring.

For example, if one parent has the genotype AA and the other has aa, the letters at the top of the Punnett square may represent the A alleles from the first parent, while the letters on the side represent the a alleles from the second parent. When combined in the squares of the grid, these alleles illustrate the potential genetic makeup of the offspring. The combinations within the squares then show the possible genotypes that the offspring could inherit.

This fundamental aspect of Punnett squares allows geneticists and students alike to predict how traits may be passed on from parents to offspring, making it a crucial tool in the study of heredity and genetics. Understanding that the letters denote the parents' alleles clarifies how traits might be inherited and helps grasp concepts such as dominant and recessive traits.