Functional classification of xenologs and conserved genes in PCC 7942. Following COG database 1,921 genes from PCC 7942 are classified into functional categories. Of them, 1,665 genes are classified in a single category. Here we show whether these genes are identified as core genes, xenologs or none of them. Xenologous genes are particularly abundant in the categories signal transduction mechanisms and cell wall/membrane/envelope biogenesis.