Figure 5

Expression of gene transcripts and OR transcripts at various ages. Grouping of gene transcripts and OR transcripts into three categories: expressed, weakly expressed and non expressed. In experiments describing adult olfactory epithelium mRNA profiles (Figure 1), total transcripts and OR genes were identified as being expressed when ~75% of the samples gave a corresponding hybridization signal above background levels. Similarly in the experiments described in this figure, we selected as threshold 3 in the case of each litter, 6 for the adults and 6 for the old rats. "Not expressed" total transcripts and "not expressed" OR genes did not show positive signal (above background) for any of the samples.