Histogram of relative expression of selected genes using real time PCR. Technical verification (left) of differentially expressed genes identified in the subject population (Caucasian males) by SAM/GSA (n = 20): CDKN1C, HRASLS3, PTGDR, CX3CR1, and SASH1. Biological verification (right) of two selected genes using independent samples not included in our subject population (Caucasian females, n = 10): CDKN1C and SASH1. Data is represented as the log base 2 relative change in gene expression (± standard error) and all expression normalized to low cotinine from the subject population samples (Caucasian males). The data labels represent the fold change in high versus low cotinine samples, all of which were statistically significant (P < 0.05). The fold change in the gene RPS29 was used as a negative control and was not significant (n.s.) between the high and low cotinine groups.