Persons 1 and 2 in Figure 1 have a child with MSUD and some children without MSUD.
Complete the Punnett square (Figure 2) to show the possible genotypes of the children.
Use the following symbols:
N = allele for not having MSUD
n = allele for MSUD

1. Determine the genotypes of Person 1 and Person 2. Since they have a child with MSUD (genotype nn), both parents must carry the recessive allele 'n'. Since they do not have MSUD themselves, they must also have the dominant allele 'N'. Therefore, both parents are heterozygous (Nn). 2. The Punnett square shows the gametes for Person 1 (N, n) on the side and Person 2 (N, n) on the top. 3. Fill in each box by combining the allele from the corresponding row and column. - Top-left box: N from Person 1 and N from Person 2 gives NN. - Bottom-left box: n from Person 1 and N from Person 2 gives Nn. - Bottom-right box: n from Person 1 and n from Person 2 gives nn.