First-person PCR and gel electrophoresis demonstration

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 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 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 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

Nonspecific Amplification Products

Extra, unwanted bands appear on gel in addition to or instead of the target product, indicating off-target amplification.

💡 6 · ✓ 6

severe

Insufficient Amplification from Polymerase Issues

Weak or absent PCR product. Primers are degraded or show primer-dimer formation at the bottom of gel.

💡 4 · ✓ 5

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

Nonspecific Bands or Primer-Dimers Due to Component Imbalance

Multiple bands or primer-dimers appear on gel despite optimized thermal cycling. Component concentrations may be promoting nonspecific primer interactions or amplification.

💡 5 · ✓ 5

moderate

PCR污染和携带污染

Unexpected products appear in negative controls or multiple samples show identical non-specific bands, indicating contamination from previous amplifications or environmental sources.

💡 4 · ✓ 7

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

Nonspecific Bands or Primer-Dimers

Multiple bands appear on gel in addition to or instead of the expected target band. Primer-dimer artifacts or nonspecific amplification products are visible, indicating lack of reaction specificity.

💡 7 · ✓ 7

moderate

Nonspecific Bands or Primer-Dimers Due to Reagent Issues

Multiple unwanted PCR products appear on gel alongside or instead of target band, caused by reagent concentration imbalances or primer design problems.

💡 4 · ✓ 4

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