Technical replicates measure variation from pipetting, instrument response, and assay handling. They are useful for detecting local setup problems but do not create independent biological evidence.
Biological replicates
Biological replicates represent independent samples, cultures, animals, donors, passages, or experimental units. They are the basis for most biological conclusions.
Controls
Controls are part of replicate planning. A plate with many samples but weak controls may produce numbers that cannot be interpreted.
Volume planning
Replicates multiply required volume. Add enough overage for dead volume, repeated dispensing, and possible reruns. Underplanning volume can force mid-experiment changes that affect comparability.
Practical checklist
- Decide technical and biological replicate counts separately.
- Include controls before sample wells consume the layout.
- Plan total reaction volume with overage.
- Avoid placing all critical wells in one vulnerable plate region.
- Record excluded replicates with reasons.
Interpretation
Replicates do not rescue a poorly designed experiment. They only help measure variation in a design that already matches the question.