Replicates and types
Replicates in biological experimentation are repeated measurements or observations that scientists make to ensure the reliability, accuracy, and reproducibility of experimental results. There are mainly three types of replicates: biological, technical, and experimental.
Here’s a simple explanation of each type, along with examples and how to recognize them:
1. Biological Replicates
Definition:
Biological replicates involve taking measurements from independent biological samples, such as different organisms or separate individuals, treated under the same experimental conditions.
Purpose:
They show biological variation between samples or individuals and help determine if observed results are generally applicable.
Example:
- You are testing the effect of a drug on plant growth. You apply the drug to five separate plants grown in identical conditions.
How to recognize:
Each replicate is biologically independent, such as different individuals, separate plants, animals, cell cultures grown separately, or samples collected from different subjects.
2. Technical Replicates
Definition:
Technical replicates involve multiple repeated measurements or assays performed on the same biological sample to test measurement precision or instrument consistency.
Purpose:
They check if your measurement methods or instruments are consistent and reliable.
Example:
- Measuring gene expression levels from one extracted RNA sample three times using the same qPCR protocol to ensure consistency.
How to recognize:
The exact same biological material or sample is repeatedly measured. Differences in technical replicates reflect measurement or instrument variability, not biological differences.
3. Experimental Replicates
Definition:
Experimental replicates involve repeating the entire experimental procedure on separate occasions or different setups, from start to finish, to ensure reproducibility of findings.
Purpose:
They test if the experiment’s conclusions can be reliably reproduced when repeated under similar or identical conditions at different times or in different labs.
Example:
- Performing an entire drug efficacy experiment, including growing new plants from seeds, applying the drug, and measuring growth, three different times to verify reproducibility.
How to recognize:
The entire experimental procedure is repeated independently. This involves new preparation, new setups, and often new timepoints or different locations.
Quick Summary to Recognize Easily:
| Type of replicate | Easy way to identify | Checks for what? |
|---|---|---|
| Biological | Different organisms or separate samples | Biological variability |
| Technical | Same biological sample measured multiple times | Measurement consistency |
| Experimental | Entire experiment repeated independently | Overall reproducibility |
Understanding these differences helps researchers make accurate conclusions, ensuring findings are reliable, reproducible, and meaningful.