What is the function of an extraction blank in the DNA workflow?

What is the function of an extraction blank in the DNA workflow?

• A. To calibrate the instrument.
• B. To measure DNA concentration.
• C. To serve as a negative control for PCR.
• D. To detect contamination introduced during the extraction process.

Answer: (D)

An extraction blank is a negative control that goes through the entire DNA extraction workflow with all reagents but no sample. Its purpose is to reveal contamination introduced during extraction, whether from reagents, the kit, lab surfaces, or handling steps. Processed alongside real samples, if DNA or an amplifiable product appears in the extraction blank, it flags contamination at or during extraction, which could compromise all results in that batch. This control is different from a PCR negative control, which is included in the PCR setup to catch contamination that occurs during amplification or after extraction. The other options don’t fit because instrument calibration uses separate standards, a blank for measuring DNA concentration would contain no DNA and isn’t a meaningful concentration control, and concentration measurement isn’t the role of an extraction blank.

An extraction blank is a negative control that goes through the entire DNA extraction workflow with all reagents but no sample. Its purpose is to reveal contamination introduced during extraction, whether from reagents, the kit, lab surfaces, or handling steps. Processed alongside real samples, if DNA or an amplifiable product appears in the extraction blank, it flags contamination at or during extraction, which could compromise all results in that batch. This control is different from a PCR negative control, which is included in the PCR setup to catch contamination that occurs during amplification or after extraction. The other options don’t fit because instrument calibration uses separate standards, a blank for measuring DNA concentration would contain no DNA and isn’t a meaningful concentration control, and concentration measurement isn’t the role of an extraction blank.