= Solution
\b[Test whether cellular drug effects persist when <actin> is protected by a <drug-resistant allele>.] Compare otherwise matched wild-type and act1-117 <biological cells> across a drug-concentration range, measuring growth or colony formation together with <actin> organization and a relevant cellular phenotype. Each strain needs a vehicle-only baseline because the mutant already has abnormal intrinsic assembly. If the resistant strain maintains its <actin> network and the normal actin-dependent functions but still develops another reproducible defect, that residual effect is a candidate <off-target drug effect>. Comparable intracellular exposure is important: resistance caused by lower uptake would not protect only the intended target.
Conversely, coordinated rescue of the <actin> and growth phenotypes supports an on-target explanation over that dose range, without proving the absence of every other molecular interaction. Reintroducing wild-type <actin> or using another independently resistant allele helps separate the <actin> substitution from unrelated <genetic background> effects. A candidate secondary target would need its own binding or functional assay and a selective rescue test. A second <actin> inhibitor giving the same phenotype is supportive but cannot alone exclude shared secondary effects.
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