TABLE 4

Classification of mutants assigned to complementation groups

No. of groupsNo. of mutationsAverage no. of alleles per groupNo. of viable mutants% of viable mutants
Previously known genes451222.712146.67
Previously undescribed loci41521.271639.02

All complementation groups were classified according to whether or not they have been previously described and whether or not the corresponding loci are required for viability (note that for new loci represented by a single allele we cannot exclude the presence of second-site mutations precluding homozygous viability of a mutation).