Genome-wide mutagenesis studies indicate that up to about 90% of genes in bacteria and 80% in eukaryotes can be inactivated individually leaving an organism viable, often seemingly unaffected. Several strategies are used to learn what these apparently dispensable genes contribute to fitness. Assays of growth under hundreds of physical and chemical stresses are among the most effective experimental approaches. Comparative studies of genomic DNA sequences continue to be valuable in discriminating between the core bacterial genome and the more variable niche-specific genes. The concept of the core genome appears currently unfeasible for eukaryotes but progress has been made in understanding why they contain numerous gene duplicates.
► Most of genes can be individually inactivated without causing death. ► Genes dispensable in normal environment are often needed under stress. ► Progress is being made in defining the core genome of bacteria but not eukaryotes. ► Duplicate genes can undergo unexpectedly fast neofunctionalization.
Journal: Current Opinion in Biotechnology - Volume 22, Issue 4, August 2011, Pages 547–551