Generation 3 (G3) Terc−/− mice under the C57BL/6, 129/Sv and SJL mixed background display skin ulceration, alopecia and hair graying, but many other age‐related disorders, including osteoporosis, body weight changes, shortened lifespan, and type II diabetes, do not appear until G4‐G6 (Rudolph et al., 1999). The gene discussed is TERC; the disease is alopecia.