Figure 1. Shortened telomeres lead to enhanced mammary gland senescence upon serial transplantation. Whole mounted glands from TER+/+ (A-C), TER+/− (D-F), and TER−/− (g1 G-I, g5 J-L) transplanted tissues from early transplant generations 1 and 2 (A,D,G,J), middle transplant generation 3 (B, E, H, K), and late transplant generations 4 and 5 (C, F, I, L). Scale bars: 2mm.