Understand the relationship
The reasoning behind the result
Frequency uses observed units
f = M/T
The numerator is the number of assayed units classified as mutant and the denominator is every eligible assayed unit in that record. A mutant lineage can contribute many observed mutant descendants.
The proportion therefore need not equal mutations per division or per replication opportunity.
Pooling adds counts before division
fpooled = ΣMi/ΣTi
Records with larger assayed totals contribute more to the pooled proportion. Averaging record percentages would assign equal weight regardless of denominator.
The ledger retains each record so heterogeneity is not hidden.
Zero is a sample outcome
Zero observed mutants gives an endpoint point estimate of zero for that assayed sample. It does not establish biological absence or a mutation probability of zero.
Detection limits, selection, phenotypic lag and classification error remain external.
Mutation frequency and mutation rate differ
A mutation arising early can create a jackpot of descendant mutants, whereas a late event may create few. Endpoint frequency depends on growth and selection after events occur.
A fluctuation-test likelihood or externally established independent events and opportunities are required for a rate calculation.
Follow the numbers
Pool unequal replicate totals
- Replicate A contains 8 observed mutants among 10,000 assayed units.
- Replicate B contains 3 among 2,000.
- The pooled mutant count is 8 + 3 = 11.
- The pooled assayed total is 10,000 + 2,000 = 12,000.
- The pooled observed frequency is 11/12,000 = 0.000916667, or 0.0916667%.
Count pooling gives the endpoint sample proportion and does not estimate mutations per division.
Quick guide
How to use this calculator
- Enter actual observed mutant and total assayed counts for each comparable record.
- Inspect each record before the pooled result; pooling adds counts before division.
- Describe the result as an observed endpoint frequency. Estimate mutation rate only with a design and model that identifies mutation events or uses a fluctuation distribution.
Calculation method
Calculation and interpretation
Preserve count denominators and record weights while making the distinction between observed mutants and independent mutation events unavoidable.
Observed mutant frequency frecord = Mrecord/Trecord; pooled observed frequency = ΣM/ΣT
Worked example
Pool unequal replicate totals
Count pooling gives the endpoint sample proportion and does not estimate mutations per division.
Observed mutant frequency frecord = Mrecord/Trecord; pooled observed frequency = ΣM/ΣT
Supported inputs
Precision and limits
Observed endpoint proportion
The output is mutant units divided by assayed units and is never relabelled as mutation rate.
Common classification
Pooled records need one compatible mutant definition, assay eligibility rule and unit denominator.
Zero is not absence
A zero observed count supplies no detection bound or biological absence claim.
No fluctuation model
Jackpots, growth, plating fraction, phenotypic lag, selection and mutation timing are not modelled.
Numerical support
Use 1–30 records with safe whole counts, at least one assayed unit per record and mutant counts no larger than record totals.
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