An isolated mutated nucleic acid molecule encoding the BMP1B receptor polypeptide wherein the molecule: (a) has a sequence which differs from that of the wild type BMPIB receptor polypeptide in that the codon encoding amino-acid residue 249 encodes arginine rather than glutamine; (b) is able to hybridize under stringent conditions to the molecule in (a); (c) is a variant of the sequence defined in (a); (d) is the complement of the molecule defined in (a), (b) or (c); or (e) is an anti-sense sequence corresponding to any of the sequences in (a)-(d). |