Fig. 4. (A) Relative expression of MyoD I mRNA in white muscle of GH-transgenic and non-transgenic Atlantic salmon at 4 and 7 months of age. Sample size equals 11 for non-transgenic salmon at 4 months, 12 for transgenic salmon at 4 months, 9 for non-transgenic salmon at 7 months and 9 for transgenic salmon at 7 months. Results are means ± s.e.m. Data were log transformed to obtain normality. Two-way ANOVA was used, assessing the effect of age (P<0.001), presence of the transgene (P=0.452) and the interaction of age and the transgene (P=0.790). Different letters and horizontal bars indicate significant differences between ages of the fish. Relative expression is the ratio of the band intensity of the gene of interest to that of the comparator gene, 18S. (B) Picture of the gel used to analyse band intensities.