PCR protocol fundamentals—hands-on operation guide

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

severe

No Band or Faint Band Due to Thermal Cycling Errors

No visible band or very faint band appears on the gel after PCR amplification. This indicates insufficient or failed amplification of the target sequence.

💡 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

Sample Fails to Amplify Despite Positive Control Success

Positive control amplifies successfully but test sample known to contain target shows no amplification; undiluted template fails while dilutions may show improved amplification

💡 3 · ✓ 5

severe

No Band or Faint Band with GC-Rich Templates

PCR fails or produces very weak amplification specifically with high GC content templates (>65%). Standard protocols work with other templates but not GC-rich sequences.

💡 3 · ✓ 4

severe

Sequence Errors in PCR Product

Sequencing of the PCR product reveals mutations, insertions, deletions, or other sequence variations compared to the original template DNA.

💡 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

severe

Sequence Errors Within PCR Product Body

Sequencing reveals point mutations, insertions, or deletions within the amplified fragment that are not present in original template.

💡 5 · ✓ 6

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

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

Incorrect Reaction Efficiency Due to Oligo Binding to Non-Molecular Biology Tubes

Variable and incorrect standard curve efficiency when using serial dilutions; effect more pronounced when same dilution series stored at 4°C and reused; inconsistent differences between amplification plots; problem resolves when different operator uses different tubes

💡 4 · ✓ 5

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

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

moderate

JumpStart Taq ReadyMix Underperforming Due to Incorrect Hot Start Protocol

JumpStart Taq ReadyMix does not work as well as similar products from different suppliers; amplification is weak or absent despite correct assay design

💡 3 · ✓ 3