Marfan syndrome can be caused by mutations in either of two genes, but mutations in one of the genes blocks activity of the other. this means that marfan syndrome demonstrates:

Answer;

-Genetic heterogeneity and epistasis.

Explanation;

-Marfan syndrome is a genetic disorder that affects the body's connective tissue that holds all the body's cells, organs and tissue together.

-Genetic heterogeneity is defined as mutations at two or more genetic loci that produce the same or similar phenotypes. Genetic heterogeneity may be either; allelic heterogeneity, which occurs when a similar phenotype is produced by different alleles within the same gene; or locus heterogeneity, which occurs when a similar phenotype is produced by mutations at different loci.

-A gene is said to be epistatic when its presence suppresses the effect of a gene at another locus. Epistatic genes are sometimes called inhibiting genes because of their effect on other genes which are described as hypostatic.

-From these descriptions the marfan syndrome demonstrates both genetic heterogeneity and epistasis.