Relative expression of BACT, H2A, B2M, GAPDH, PGK1, S18, and UBC at different stages of porcine embryonic development. Top row: regulated genes; bottom row: stably expressed genes. X-axis: developmental stage (GV = germinal vesicle stage, M2 = metaphase-2 stage, 2C = 2-cell stage, 4C = 4-cell stage, CB = early cavitating blastocyst, EB = expanded blastocyst). Y-axis: normalized relative expression. Data was normalized to the geometric mean of 4 stably expressed genes (18S, PGK1, GAPDH, UBC) as determined by geNorm analysis. For each developmental stage, the normalized expression value was subsequently divided by the normalized expression value of the germinal vesicle stage. Error bars represent SEM.