Punnett Squares When we know information about the genetic makeup of two parents, we can predict the genetic makeup of any possible offspring created between them using a punnett square.

There are steps to follow to answer a punnett square problem. We will use the example question to go through each of the steps.

Example 1 In bunnies, long ears are dominant over short ears. Using a Punnett Square, predict the genotype and phenotype percentages of the offspring between a homozygous long eared (EE) bunny and a short eared bunny (ee).

Step 1 Choose a letter to represent the trait (if not already given). E – dominant trait = long ears e – recessive trait = short ears

Step 2 Write down the genotype (genes) of each parent. EE x ee

Step 3 Draw a punnett square (it looks like a window!). Write the genes of one parent across the top and the other down the side. EE e e

Step 4 Fill in each box in the punnett square by taking the gene from the top and he one from the side. EE e e Ee

Step 5 Answer the question. Genotypes: 4/4 Ee or 100% Ee (heterozygous long ears) Phenotypes: 4/4 or 100% Long ears