TABLE 1

Lethal mutations detected in the mutation-accumulation experiments

GenerationTotal  chromosomesLethal  chromosomesMutation  rate (%)
Experiment 1
10 52112.38
17 37 20.79
25 27 73.75
35 17 21.25
Total133222.17
Experiment 2
9–11 69 50.75
19–21 58 50.90
29–31 49 92.09
39–41 45 20.40
Total221211.00
Experiment 3
9–11 77 70.95
20–22 58 81.35
29–31 47 61.59
Total182211.38
• Only lethal mutations that arose since the previous assay generation are included. The lethal mutation rate was calculated by equating the observed frequency of nonlethal chromosomes to the first term of a Poisson distribution, whose mean is the product of the mutation rate and the number of generations since the last assay generation. For experiments 2 and 3, where sets of three different generations are pooled, this number is equated to the generation number of the middle member of each set. The total mutation rates for each set were calculated using the mean number of generations over the set.