Formulas
Viable Cell Count
Final Concentration x Dilution Factor = Initial Concentration (cfu/ml)
Final Concentration = number of colonies/ dilution (ml)
Dilution Factor = 1/ dilution (ml)
Mutant Concentration
Number of Colonies/ dilution (ml)
Spontaneous Mutation Frequency
Mutant Concentration/ Viable Cell Count = (mutants/ viable cell count)
Chi Square (Null hypothesis; Re-spread and non-re-spread should be equal)
x^2 = Sum of all ((Observed - Expected)^2 / Expected)
Calculations
Viable Cell Count
Neelo Mohsan Cullen Isha
1680 x (10^6) 4000 x (10^6) 1680 x (10^6) 1720 x (10^6)
1.68 x 10^9 cfu/ml 4.0 x 10^9 cfu/ml 1.68 x 10^9 cfu/ml 1.72 x 10^9 cfu/ml
Average = 1.68 x 10^9 + 1.68 x 10^9 + 1.72 x 10^9 = 5.08 x 10^9 / 3 = 1.7 x 10^9 cfu/ml
Mutant Concentration
Neelo Mohsan Cullen Isha
4 x 10 42 x 10 4 x 10 5 x 10
40 mutants/ml 420 mutants/ml 40 mutant/ml 50 mutants/ml
Average = 40 + 40 + 50 = 130 / 3 = 43 mutants/ml
Spontaneous Mutation Frequency
Neelo Mohsan
(40 mutants/mL)/ (1.68 x 10^9 cfu/mL) (420 mutants/ml)/ (4.0 x 10^9 cfu/ml)
2.3 x 10^-8 mutants/ viable cell count 1.05 x 10^-7 mutants/ viable cell count
Cullen Isha
(40 mutants/mL)/ (1.68 x 10^9 cfu/mL) (50 mutants/mL)/ (1.72 x 10^9 cfu/mL)
2.3x 10^-8 mutants/ viable cell count 2.9 x 10^-8 mutants/ viable cell count
Average = 2.3 x 10^-8 + 2.3 x 10^-8 + 2.9 x 10^-8 = 7.5 x 10^-8 / 3 = 2.5 x 10^-8 mutant/ viable cell count
Chi Square
(10-4)^2 / 4 + (10-4)^2 / 4 + (10-5)^2 / 5 = 9 +9 + 5 = 23 = x^2
Degrees of freedom = 1
p value = 0.0001
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