Question

In a group of humans, some individuals have Marfan syndrome and others do not. In this group, the gene for the Marfan syndrome trait has two alleles. The allele for having Marfan syndrome (M) is dominant over the allele for not having Marfan syndrome (m). Braden, a human from this group, has Marfan syndrome. Based on Braden's phenotype for the Marfan syndrome trait, which of the following could be Braden's genotype for the Marfan syndrome gene?

Answer 1

Allele M causes Marfan syndrome and M is dominant, so even if there's an M and an m, that individual would have Marfan syndrome. This means Braden could have Mm or MM.