A comparative study of duplications in bacteria and eukaryotes: the importance of telomeres

The genomes of three bacteria (Haemophilus influenzae, Mycoplasmagenitalium, and Escherichia coli) and two eukaryotes (Saccharomycescerevisiae and Caenorhabditis elegans) were compared. The distribution oftheir putative open reading frames (ORFs) was studied, and severalconclusions were drawn: (1) All of these genomes, even the smallest,exhibit a significant proportion (7%-30%) of duplicated ORFs. Thisproportion is a function of genome size and appears unrelated to thebacteria/eukaryote division. (2) Some of these ORFs constitute families ofup 20 or more members. (3) The levels of sequence similarity within thesefamilies are highly variable and their distribution is different amongbacteria and eukaryotes. (4) In yeast, there are topological relationshipsbetween members of the same family. The paired ORFs are frequently in thesame orientation with regard to their respective telomeres and located atcomparable distances from them.