Separate relative descendants from inherited-state loss

Define the evidence

Changes in the frequency of a genetic state can reflect differential reproductive contribution, state transmission, mutation, transfer or changing population composition. These mechanisms are not interchangeable. Selection changes representation of existing variation; it does not require a future benefit to direct the creation of that variation.

Connect mechanism and measurement

The original marker is a neutral symbolic label for bookkeeping, not a resistance determinant or actual engineered trait. Initially its frequency is 0.4. In the stipulated comparison, carriers contribute a times as many descendants per initial cell as noncarriers, whose weight is one. Before state loss, carrier-descendant frequency is q=0.4a/(0.4a+0.6). These are supplied relative contributions, not instructions to optimize microbial growth.

Only after descendant contributions are normalized does the model retain the marker in fraction b of carrier descendants. Final marker frequency is qb, and the lost fraction q(1−b) joins noncarriers. Population fractions still sum to one. The loss stage can represent an abstract inheritance failure without specifying an element, maintenance system or manipulation method.

If final frequency is below the initial 0.4, that does not by itself prove carriers had lower reproductive contribution: sufficiently large state loss can outweigh their higher contribution. Conversely, a final increase does not prove a new mutation arose. Actual resistance evidence would additionally need defined phenotype, context and ancestry; this symbolic calculation supplies no clinical or antimicrobial recommendation.

Reconstruct the original record

At relative contribution a=1.5, carrier descendants before loss are 0.6/(0.6+0.6)=0.5. Retention b=0.75 leaves frequency 0.375 and transfers 0.125 of the whole population into the noncarrier class. The final fraction falls below 0.4 despite higher carrier contribution.

Predict and investigate

Predict first: Can carrier contribution be higher while the final marker frequency decreases?

Change the two stages separately and reconstruct both denominators. Identify whether a difference arises before or after normalization; do not attribute the final result to a new mutation that the model excludes.

Defend a changed case

Apply the mechanism to a changed boundary

Use relative contribution 0.5 and perfect retention. Find the final carrier and noncarrier fractions.

Retain the first response, units, uncertainty and any prior feedback exposure in the notebook before comparing this public explanation.

Compare a worked response

The carrier contribution is 0.2 out of total 0.8, so q=0.25. Perfect retention leaves 0.25 carriers and 0.75 noncarriers; there is no state loss or new mutation in this case.

Retain bounded evidence

Preserve original assumptions, first responses and feedback exposure in the Microbiology evidence workspace. All numerical records are original fictional evidence. No culture, genetic modification, transfer execution, resistance generation or personal clinical interpretation is requested. Actual independent practical competence is not established.

Primary mechanism context, checked 30 October 2026. Original teaching and fictional data; no copied operating procedures.