A Punnett square is a chart that shows the likelihood of all of the possible allele combinations that result from a genetic cross. Punnett Squares help show the probability that an offspring will receive a particular combination of alleles. Probability is the likelihood that particular outcomes will occur.
This Punnett square is used to predict the probability of a pea plant producing purple or white flowers.
The top purple flower has allele combination Bb and represents the male genotype. The side purple flower has allele combination Bb and represents the female genotype. Each box in the middle represents a possible allele combination when the two parents are paired. The offspring received one allele from each parent.