Fig. 2.

The distribution of fitness effects caused by gene deletions. The filled and empty bars indicate lethal and neutral effects, respectively. The dotted bars indicate an arbitrarily delimited interval of deleterious effects. The distribution was obtained by making use of data published elsewhere (35). The relative fitness was calculated as a number of cell doublings completed by a deletion strain in relation to an average number of doublings in a culture containing all viable deletions. For this reason, the modal value of fitness is higher than one. For more information, consult www-deletion.stanford.edu/YDPM.