Punnet squares are used when doing a problem dealing with genetics. They are good for figuring out probabilities of characteristics appearing in future generations.

For example: If a woman with homozygous dominant wavy hair is crossed with a man that has homozygous recessive strait hair. What is the percentage of the kids that are expected to have wavy hair?

Because all of the possibilities are heterozygous, they would still contain the dominant feature. So 100% of the kids should have wavy hair.

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