Digital Differential Display

A nice feature of the NCBI UniGene page is Digital Differential Display (DDD). DDD indirectly compares gene expression levels in different tissue types by comparing the number of ESTs identified during the random sequencing of cDNA libraries. Statistical tests are used to determine whether observed differences in the expression of a particular gene are nonrandom. You pick the libraries you wish to compare, and the program finds statistically significant differences in cDNA representation between (or among) the libraries. Here's a link to one I did comparing Drosophila head and embryo cDNA libraries. Genes important for eye function, such as arrestin and ninaE, are overrepresented in the head library, while genes important for embryonic development, such as lola and armadillo, are overrepresented in the embryonic library. Cool!