_:vb50944020 . _:vb50944020 . _:vb50944020 . _:vb50944020 "url:https://www.ncbi.nlm.nih.gov/pubmed/20683927"^^ . _:vb50944020 . _:vb50944020 . _:vb50944020 "A brachydactyly type A1 has_material_basis_in homozygous or heterozygous mutation in the GDF5 gene on chromosome 20q11."^^ .