punnett square – a grid used to predict what genes offspring might inherit from their parents

(Pronounced puh-nit)

To remember the meaning of punnett square, use the following mnemonic:

He punted it (punnett) into the gridiron (grid) wearing jeans (genes). 

A punnett square is essentially a grid that shows all the potential combinations of alleles (different versions of a gene) that offspring could inherit from their parents. To create a punnett square, you place one parent's alleles along the top and the other parent's alleles down the side, then fill in the boxes to show every possible combination. This tool helps you work out the probability of offspring having certain characteristics or genotypes. 

Example

Mendel’s green pod and yellow pod experiment shows how the parent pods could still pass on the yellow trait even when they were green pods. He called the green pod trait the dominant trait and the yellow pod the recessive trait.

Parent 1

Is a green pod but has a yellow pod allele from one parent and a green pod allele from the other.

Parent 2

Is a green pod too and also has a yellow pod allele from one parent and a green pod allele from the other.

The probability is that there is a 75% chance this generation of pea pods will have green pods and 25% chance they will have yellow pods.