Why did my Cloning fail?

Playbooks

• Cloning: no coloniesTransformation plate shows no colonies (or far below expected CFU).
• Cloning: empty vectorColonies grow but screened clones lack the insert (vector only).
• Cloning: wrong insertScreened clones contain an insert of unexpected size or sequence.
• Cloning: satellite coloniesTiny satellite colonies surround larger colonies on antibiotic plates.
• Cloning: low transformation efficiencyColonies appear but CFU is far below the competent-cell rating or lab baseline.

Calculators

• Molarity converterConvert between nM, µM, mM, and M.
• Dilution (C1V1)Solve C1V1 = C2V2 and plan serial dilutions.
• Master mix scalerScale PCR/qPCR master mix with overage.
• Buffer recipesStandard bench buffers with per-liter amounts.

FAQ — Cloning

No colonies

Transformation plate shows no colonies (or far below expected CFU). Transform a known-good plasmid on the same competent cells and plate batch — Controls-first split between cells/plates vs ligation chemistry. Pour fresh antibiotic plates at the validated concentration; check expiry — Over-strong or degraded antibiotic is a classic zero-colony cause. Re-ligate with a fresh insert:vector ratio and include a no-insert control — Confirms assembly chemistry before changing transformation parameters. Use standard heat-shock (42 °C / 30–45 s) and SOC recovery 1 h at 37 °C — Recovers many protocol-drift failures.

Empty vector

Colonies grow but screened clones lack the insert (vector only). Re-digest vector longer; gel-purify linear band; phosphatase-treat sticky ends — Cuts the uncut/re-ligation background that floods empty clones. Re-prep insert; confirm concentration and size before ligation — Invisible/degraded insert presents as all-empty screens. Set insert:vector ≈ 3:1 molar and include a no-insert control plate — Ratio and control plate quantify how much empty background to expect.

Wrong insert

Screened clones contain an insert of unexpected size or sequence. Re-amplify insert; verify size on gel against ladder before ligation — Stops wrong-band excision from propagating into clones. Confirm oligo IDs/sequences against the design file; re-order if mismatched — Oligo mix-ups look like successful cloning of the wrong thing. Sequence 2–3 colonies across the junctions before scaling minipreps — Catch wrong inserts before investing in midiprep/expression.

Satellite colonies

Tiny satellite colonies surround larger colonies on antibiotic plates. Pour fresh plates at the validated antibiotic concentration; store cold and use promptly — Degraded antibiotic is the usual satellite driver. Pick large colonies early; avoid incubating amp plates overnight-plus — Limits local antibiotic breakdown around true transformants. Dilute transformation before plating to reduce CFU density — Fewer true colonies means less secreted β-lactamase rescue.

Low transformation efficiency

Colonies appear but CFU is far below the competent-cell rating or lab baseline. Thaw a fresh competent-cell aliquot on ice; avoid re-freezing — Partial competence loss is the top efficiency drop cause. Use ≤10% ligation volume in the transformation or purify DNA first — Excess salts/enzymes suppress competence. Standardise heat-shock to 42 °C / 45 s with SOC recovery 1 h — Recovers many protocol-drift efficiency losses.