We hypothesize that gene expression in the CBs of these two strains of mice are divergent thus contributing to the disparity in the phenotypes. More specifically, (1) genes related to CB function are expressed less in the A/J mice compared to DBA/2J mice; (2) gene expression levels of morphogenic and trophic factors of the CB maybe significantly lower in the A/J mice than the DBA/2J mice. In order to test these hypotheses, we utilized microarray analysis to examine transcriptional differences between CBs of both strains of mice. Keywords: comparative expression profiling Overall design: . This study utilizes microarray analysis to test these hypotheses. Three sets of CBs were harvested from both strains. RNA was isolated and used for global gene expression profiling (Affymetrix Mouse 430 2.0 array). Statistically significant gene expression was determined as a minimum 6 counts of 9 pairwise comparisons, minimum 1.5-fold change, and p < 0.05.