Overview

Marfan Syndrome is an autosomal dominate genetic defect.  It affects the Fibrillin-1 gene which is located on the chromosome 15q1.5----q2.1.^[1] 

Probablility 

If neither parent is a carrier of the disease, there is no chance of inheriting Marfan syndrome; but not impossible to have.  A mutation of fibrillin-1 will cause marfans syndrome.

If one parent posesses the allele than its 50/50 whether the offspring will portray the phenotype

     this is because its a dominate allele.  It only takes 1 to posess the phenotype. 

If both parents have the phenotype it is a 100 percent chance the offspring will have the phenotype.  

 ^[2]