COMPLETE GENOME SEQUENCES OF CELLULAR LIFE FORMS - GLIMPSES OF THEORETICAL EVOLUTIONARY GENOMICS

The availability of complete genome sequences of cellular life forms c reates the opportunity to explore the functional content of the genome s and evolutionary relationships between them at a new qualitative lev el. With the advent of these sequences, the construction of a minimal gene set sufficient for sustaining cellular life and reconstruction of the genome of the last common ancestor of bacteria, eukaryotes, and a rchaea become realistic, albeit challenging, research projects. A vers ion of the minimal gene set for modern-type cellular life derived by c omparative analysis of two bacterial genomes, those of Haemophilus inf luenzae and Mycoplasma genitalium, consists of similar to 250 genes. A comparison of the protein sequences encoded in these genes with those of the proteins encoded in the complete yeast genome suggests that th e last common ancestor of all extant life might have had an RNA genome .