Gene expression shows a biased chromosomal distribution. Distribution was generated based on either the number of genes (A & B, upper panel) or the number of tags (A & B, lower panel). (A) The fraction of observed germline (black) and soma (gray) expressed genes compared to the expected value per chromosome is plotted (upper panel). The expected value is based on a random distribution of expressed genes throughout the genome as described in Methods. To compare expression levels of expressed genes on each chromosome (measured by the number of SAGE tags; lower panel), the average number of tags per gene in each gene set was first calculated then was multiplied by the number of genes observed in the same gene set for each chromosome to obtain the expected total number of tags (expression level) per chromosome. (B) Two sets of germline-expressed genes are compared; germline-expressed genes that are enriched or specifically expressed in the germ line (black), and germline-expressed genes that are expressed at a similar or higher level in the soma, as compared to the germ line (gray). The fraction of expressed genes compared to the expected value (upper panel), and the level of expression (lower panel), were determined as in (A). Statistical significance is marked by an asterisk (P < 0.001; hypergeometric probability test for the number of genes; re-sampling method for the number of tags, see Methods for details).