Figure 3. (A) Constitutive protein expression of ACTB (control), ATM, BRCA1, BRCA2, MLH1, RAD51, and TP53 in untreated fibroblasts of the affected vs. the healthy twin. Relative protein expression (z ratio normalized by log10 transformation and z scores) was measured by antibody microarrays using three biological replicates. Note the decreased BRCA1 level (75% expression ratio) in the affected twin. (B) Differential induction of BRCA1 protein in fibroblasts of the healthy twin (gray bars) and the affected twin (black bars) at 1 h and 4 h after 1 Gy γ-irradiation. Relative protein expression in treated vs. untreated cells of each twin was measured by antibody microarrays using three biological replicates.