A cleft chin is an inherited trait. Wherever a gene pair contains the dominant allele (e.g., $B$), you can expect a cleft chin phenotype.

Cleft Chin Phenotype

You can expect a smooth chin phenotype only when there are two copies of the recessive allele (e.g., $bb$).

Smooth Chin Phenotype

In a Punnett square, a capital letter represents the dominant allele, and a lowercase letter represents the recessive allele.

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The Punnett square shows different combinations of alleles that can be inherited from parents. Capitalized letters used in Punnet squares denote dominant alleles, while the lowercase letters denote recessive alleles. In this case "B" is a dominant allele and "b" is a recessive allele.

Punnett Square

Spielman, R. M., Jenkins, W. J., & Lovett, M. D. (2020, April 22). Psychology (2nd ed.). OpenStax. https://openstax.org/books/psychology-2e/pages/1-introduction

OpenStax Psychology (2nd ed.) Textbook

In the Punnett square below, say "B" is a dominant allele representing having a cleft chin, while "b" is a recessive allele representing not having a cleft chin. In this case, what is the probability that the child, represented in the white squares, will not have a cleft chin?

A Punnett square can be used to display the possible genetic outcomes when two heterozygous parents (Np) mate. This specific cross results in four potential allele combinations for their offspring: one homozygous dominant (NN), two heterozygous (Np), and one homozygous recessive (pp).

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