Punnett square: A genetics puzzle

In this Punnett square, the colour green in unripe pods is determined by the dominant allele ‘G’ and the colour yellow in unripe pods is determined by a recessive allele ‘g’.

The little four-square grid we drew in school while learning about genetic crossing has a name: the Punnett Square. These squares are a way to predict the possible genetic outcomes of the offspring when two individuals with known genotypes are crossed.

The Punnett Square is named after British geneticist Reginald Punnett. Drawing these squares is simple. Imagine a grid, usually with four squares. Along the top and side of the grid, you list the possible genetic traits of one parent on one side and the other parent on the other side. Then, you fill in the squares by combining the traits from each parent. Each square effectively represents a possible combination of traits that their offspring could inherit. It’s a simple way to visualise the probabilities of different traits showing up in the offspring.

Punnett Squares are commonly used in biology to understand inheritance patterns, like when you learn about dominant and recessive genes in school.

A Punnett Square is a useful tool that helps predict the variations and probabilities resulting from cross-breeding. It is often used to study the outcomes of cross-breeding but it can also be used to understand the genetic traits in the offspring of animals, including humans. Researchers typically use them together with Mendelian inheritance, a fundamental concept in genetics discovered by Gregor Mendel.