Figure 3. A FBN1 mutation in exon 18. A-C: A heterozygous A>G transition (indicated by the arrow) resulted in the substitution of tyrosine by cysteine (Y754C) in the proband, patient II:3 and III:3 respectively. D-F: The corresponding normal sequence in the unaffected family member II:5, III:1, and spouse II:4, respectively. G: The corresponding normal sequence in a healthy control. H: The sequence alignment of FBN1 orthologs surrounding mutated site using ClustalW. The tyrosine⁷⁵⁴ of human FBN1 protein is highly conserved in several species. These sequences were selected from the NCBI database.