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Molecular Biology Bilibili (China-Accessible Mirrors)

First-person PCR and gel electrophoresis demonstration

🚨 Failure Case Library (20) + Submit your own case

critical
No Band Due to Incorrect Component Concentrations
No visible band or very faint band on gel despite proper thermal cycling parameters. The reaction components may be at suboptimal or inhibitory concentrations.
💡 5 · ✓ 5
critical
No Band or Faint Band Due to Incorrect Component Concentrations
PCR amplification fails or produces very weak bands. Thermal cycling parameters appear correct, but reaction components may be improperly balanced or missing.
💡 6 · ✓ 6
critical
Complete Absence of PCR Product
No bands visible on agarose gel after PCR amplification, indicating complete reaction failure.
💡 6 · ✓ 6
critical
No Band Due to Omitted Critical Components
Complete absence of PCR product on gel due to missing essential reaction components, representing a critical setup error.
💡 5 · ✓ 5
critical
No PCR Product Detected
Gel electrophoresis shows no visible band at the expected product size after PCR amplification, indicating complete reaction failure.
💡 8 · ✓ 8
severe
No Band Due to Template or Reagent Quality Issues
PCR fails to produce visible band despite correct concentrations and cycling parameters. Template degradation, contamination, or impure reagents may be inhibiting the reaction.
💡 5 · ✓ 5
severe
No Band or Faint Band Due to Thermal Cycling Issues
After PCR amplification and gel electrophoresis, no visible band appears at the expected product size, or only a very faint band is observed, indicating insufficient or failed amplification.
💡 6 · ✓ 6
severe
No Band or Faint Band Due to Reagent Concentration Issues
Gel shows no amplification product or very weak bands despite correct thermal cycling parameters, indicating problems with reaction component concentrations.
💡 6 · ✓ 6
severe
No Band or Faint Band Due to Suboptimal Thermal Cycling Parameters
No visible PCR product band appears on the gel, or only a very faint band is detected. This occurs despite using appropriate template and primers, suggesting insufficient amplification.
💡 6 · ✓ 6
severe
Incorrect PCR Product Size
Gel electrophoresis shows PCR product band(s) at unexpected molecular weight, either larger or smaller than the predicted amplicon size.
💡 3 · ✓ 4
severe
Multiple or Non-Specific PCR Products
Gel electrophoresis reveals multiple bands, smearing, or bands at incorrect sizes in addition to or instead of the expected product, indicating lack of amplification specificity.
💡 7 · ✓ 7
severe
Low or No Amplification Due to Template Issues
PCR yields little to no product visible on gel electrophoresis. Expected band is absent or extremely faint despite using standard reaction conditions.
💡 6 · ✓ 6
severe
No Product Due to Suboptimal Cycling Parameters
No amplification product visible despite proper template and reagents, suggesting thermal cycling conditions are inappropriate.
💡 4 · ✓ 4
moderate
Smeared Bands on Gel
PCR products appear as continuous smears rather than discrete bands on gel, indicating template degradation, excessive cycling, or nonspecific amplification throughout a size range.
💡 5 · ✓ 5
moderate
Smeared Bands Due to Template Quality or Concentration Issues
Gel displays smeared bands suggesting degraded products or heterogeneous amplification. Template-related issues such as degradation, contamination, or excessive concentration are suspected.
💡 6 · ✓ 6
moderate
Nonspecific Amplification and Smearing on Gel
Gel shows multiple bands, smears, or high background instead of single clean product band. May include primer-dimers at bottom of gel.
💡 6 · ✓ 6
moderate
Smeared Bands Due to Excessive Thermal Cycling
Gel shows smeared or diffuse bands rather than discrete sharp bands. The smearing pattern suggests heterogeneous product populations from excessive amplification or nonspecific priming.
💡 6 · ✓ 6
moderate
Nonspecific Bands or Primer-Dimers Due to Thermal Cycle Issues
Gel shows multiple bands instead of single target band, or primer-dimers appear as small molecular weight products. The desired product may be present but accompanied by unwanted amplification artifacts.
💡 6 · ✓ 6
moderate
Excessive DNA Smearing on Gel
Amplified DNA appears as broad smear rather than discrete bands, indicating degradation or over-amplification artifacts.
💡 8 · ✓ 8
moderate
Amplification Failure from Suboptimal Cycling Parameters
No product or very weak bands despite proper template and primer quality. Reaction components appear functional in other assays.
💡 4 · ✓ 4
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