Practice question

Primer-dimer formation occurs when primers anneal to each other due to 3' complementarity and are extended by polymerase, generating short spurious products. These dimers consume limited primers, dNTPs, and polymerase activity, reducing availability for genuine target amplification. On agarose gels they appear as diffuse low-molecular-weight bands below 100 base pairs, and in real-time PCR they elevate background fluorescence and produce non-specific melting peaks. High primer concentration, low annealing temperature, and poor design exacerbate phenomenon, leading to failed assays and misleading quantification.