For example,nearly all patients with classic achondroplasia contain the same Gly380Arg (G →C) substitution in FGFR3 (Horton et al., 2007).This Gly380Arg substitution leads to a constitutively active FGF receptor that isthought to confer a selective advantage to spermatogonial cells (Tiemann-Boege et al., 2002; Choiet al., 2008). The gene discussed is FGFR3; the disease is achondroplasia.