Based on this information, what is Madelyn's phenotype for the Thomsen disease trait?

 - not having Thomsen disease
 - having Thomsen disease
Madelyn's genotype for the Thomsen disease gene is MM. Madelyn's genotype of MM has only M allelles. The M allele is for having Thomsen disease. So, Madelyn's phenotype for the Thomsen disease trait must be having Thomsen disease.
To check this answer, consider whether Madelyn's alleles are dominant or recessive. The allele for not having Thomsen disease (m) is recessive to the allele for having Thomsen disease (M). This means M is a dominant allele, and m is a recessive allele.
Madelyn's genotype of MM has two dominant alleles. An organism with at least one dominant allele for a gene will have the dominant allele's version of the trait. So, Madelyn's phenotype for the Thomsen disease trait must be having Thomsen disease.