Summary of the results obtained in the site-directed mutagenesis experiment^a.

apl, pd, pn: fraction of lethal, deleterious, and neutral mutations, respectively. : mean selection strength. V(s): variance of mutational fitness effects. Sub-indexes v and d refer to all viable mutations and deleterious (non-lethal) mutations, respectively. pl, , V(s), , and V(sv) were obtained directly from the data. and V(sd) were estimated by non-linear regression from negative s-values only and used to infer pd and pn (95% confidence intervals are shown in these cases).