Figure 4From: Extensive molecular differences between anterior- and posterior-half-sclerotomes underlie somite polarity and spinal nerve segmentationStatistical significance of differential gene expression in the array data. Fisher's exact test was used to explore the null hypothesis that known differentially-expressed genes are not related to their expression values in A- versus P-half-sclerotome. The y-axis shows the probability (p) that a pool of transcripts shows no enrichment of differentially-expressed genes; the lower the p-value the more likely it is to have significant enrichment. The x-axis shows the rank-ordered pool size of transcripts as determined by statistical certainty of differential expression in ascending order. The inset shows an expanded view of the rectangle indicated close to the origin. The dotted line corresponds to p = 10-9. The maximum statistical significance, and thus the minimum estimate for the total number of genes that are differentially-expressed between the two sclerotome halves, is obtained with a pool of ~175 transcripts.Back to article page