TABLE 1

Mutational saturation

Times hit (n)Chromosome 3 genes in DfaN = 483, λ = 0.558b613 λ = 0.241, 115 λ = 1.51cN = 111, P = 0.0714dChromosome 2 genes in DfaN = 577, λ = 0.600b680 λ = 0.331, 110 λ = 2.08cN = 202, P = 0.0374d
02765070.03175020.0
11541541540.01901901900.17
2434343.00.17575756.50.64
3168.015.70.491911.423.61.6
461.15.61.01171.711.02.9
550.11.71.750.24.54.3
6–121400.5213.62702.125
>12400.00.94500.01.1
  • a The number of genes located within available deficiencies on the indicated chromosome that were hit one, two, three, etc., times by verified single insertions within the strains analyzed. The deficiencies remove ~60% of chromosomes 2 and 3.

  • b The predicted values from a model of a single mutability class (N, number of genes; λ, Poisson parameter). The fit to the observed data is poor: for just n = 1–5, χ2 = 270, Embedded Image (chromosome 3) and χ2 = 263, Embedded Image (chromosome 2). After correcting for the contributions from hotspots according to columns 5 and 9, the corresponding values still fit poorly: χ2 = 20, Embedded Image (chromosome 3) and χ2 = 36, Embedded Image (chromosome 2).

  • c The number of genes hit one to five times predicted by the sum of two Poisson distributions that model the coldspot and warmspot classes. For both mutability classes the first number corresponds to the total number of genes and the second number to the Poisson parameter λ. The parameters were determined using an Excel spreadsheet that allowed the distributions to be modeled using numerical methods. Genes hit >5 times are strong hotspots that are not modeled by the two predicted mutability classes. The fits after correcting for contributions from hotspots according to columns 5 and 9, for n = 1–5 are quite good: χ2 = 0.81, Embedded Image (chromosome 3) and χ2 = 3.8, Embedded Image (chromosome 2).

  • d The estimated number of genes hit 1–5 times contributed by hotspot genes. Hotspot genes hit between 6 and 12 times were assumed to be a uniform class and modeled using a binominal distribution. There were 14 such loci on chromosome 3, while on chromosome 2 there were 25 loci, after subtracting the 2 loci in this category contributed by warmspot genes.