Jacob calls his friend Mark to tell him the news, and to Jacob's surprise, Mark has heard of MSUD. In fact, Mark says that his wife is a carrier so he got tested to see if he was a carrier as well. After getting tested, Mark and his wife decided to have children because there was no increased risk of their child getting MSUD. Based on this information, Mark and his wife must have the genotype: g

Explanation:

Since Mark's wife was a carrier, it means that she is heterozygous for the trait. And after Mark got tested, they decided to have children due to no increased risk if they do have children, it means the condition is not an autosomal dominant condition but a recessive condition because if the condition is dominant, only one copy of the affected allele is needed to increase risk.

Thus, with a no increased risk, it means Mark is normal i.e. carries no copy of the recessive allele.