The Punnett square

The Punnett square graphically illustrates the basic rules of heredity. It is a pictorial genetic diagram in a grid form.

Punnett squares illustrate the basic rule of heredity

He punted (Punnett) the ball into the gridiron (grid).

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 one shows it has the yellow allele from one parent and a green allele for 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.

Parent 2 also has a green pod but a yellow allele from one parent and a green for the other

Punnett square showing there is a 75% chance of green pods being inherited where 25% will be yellow

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.