How long do DNA samples last?
How Long Do Samples for DNA Testing Last?
DNA testing is widely used for paternity testing, relationship DNA testing, and forensic investigations, but how long does a DNA sample remain viable for testing? The lifespan of a DNA sample depends on the type of sample, how it is collected, and storage conditions. Properly stored samples can last for weeks, months, or even years, depending on the source. In this guide, we’ll break down how long different DNA samples last and how to preserve them for the most accurate results.
How Long Do Buccal (Cheek Swab) DNA Samples Last?
Buccal swabs are the most commonly used DNA sample for relationship DNA testing, including paternity, sibling, and grandparent DNA tests. They are simple to collect, painless, and highly effective in preserving DNA.
Lifespan: If stored properly, buccal swabs can last up to 6 months at room temperature. In refrigerated conditions, they can remain viable for over a year.
Storage Tips:
Allow the swabs to air dry before sealing them in a paper envelope (plastic can trap moisture and cause DNA degradation).
Keep them in a cool, dry place, away from sunlight and humidity.
Avoid eating, drinking, or smoking 30 minutes before collecting a sample to prevent contamination.
For best results, buccal swabs should be sent to the lab as soon as possible, but they can still be used effectively months later if stored correctly.
How Long Do Forensic DNA Samples Last?
Forensic DNA samples, often used when a buccal swab isn’t available, include hair, blood, and items like toothbrushes or clothing. These samples have varying lifespans depending on how they are stored.
Hair with Root
Lifespan: DNA from hair roots can last for years, sometimes decades, if stored properly.
Storage Tips: Keep in a dry, room-temperature environment in a paper envelope.
Blood Stains
Lifespan: Dried blood can retain DNA for years when stored in cool, dry conditions.
Storage Tips: Avoid excessive heat or moisture, which can degrade the sample.
Toothbrushes
Lifespan: DNA can be detectable for months to years, depending on usage and storage conditions.
Storage Tips: Let the toothbrush dry before storing in a paper bag to prevent mold growth.
Clothing and Fabric
Lifespan: DNA from bodily fluids can remain detectable for weeks to months, but washing or environmental exposure can degrade it quickly.
Storage Tips: Store in a dry, dark place and avoid excessive handling.
Forensic samples may take longer to process (5-7 business days) compared to buccal swabs due to the additional steps needed for DNA extraction.
How Long Do DNA Samples Last for Infidelity Testing?
Infidelity DNA testing analyzes semen, saliva, or other bodily fluids found on personal items such as clothing, bedding, or tissues. These biological materials degrade faster than other DNA sources.
Semen and Saliva on Fabric: DNA remains detectable for weeks to months if dried and stored properly.
Used Tissues or Wipes: DNA can degrade within days to weeks, especially in humid or warm conditions.
Clothing and Underwear: Dry samples may last for months, but washing significantly reduces DNA detection.
Best Practices for Preserving Infidelity Testing Samples:
Avoid washing the item before testing.
Store in a paper envelope, not plastic, to prevent moisture buildup.
Keep in a dry, room-temperature location to slow down DNA degradation.
Due to the fragile nature of these samples, infidelity DNA tests take 5-7 business days for processing.
Factors That Affect DNA Sample Lifespan
Several factors influence how long DNA samples remain viable:
Moisture: High humidity and water exposure can cause bacteria or mold to degrade DNA.
Heat & Sunlight: Prolonged exposure to heat or UV rays can break down DNA strands.
Handling & Contamination: Touching a sample with bare hands can introduce foreign DNA or degrade existing DNA.
Storage Method: Paper envelopes preserve DNA better than plastic bags, which can trap moisture.
Preserving DNA Samples for Accurate Testing
The longevity of a DNA sample depends on the type of sample, how it’s stored, and environmental factors. Buccal swabs remain viable for months, while forensic and infidelity samples require careful storage to prevent degradation. Understanding how to preserve DNA samples properly ensures accurate and reliable testing results.
