Unrecognised DNA Degradation in Flash-Frozen Genetic Samples in Natural History Collections

Area of Science:

• Genetics
• Molecular Biology
• Biobanking

Background:

• Optimal tissue preservation is crucial for genetic resource banking.
• Flash freezing is the current gold standard for tissue preservation.
• Field preservation methods require further investigation for DNA quality.

Purpose of the Study:

• To compare DNA preservation quality from different field preservation techniques.
• To assess DNA degradation in archival tissue collections.
• To identify optimal methods for preserving DNA integrity in field samples.

Main Methods:

• Compared DNA metrics from flash-frozen, ethanol-fixed, and lysis buffer-fixed tissues.
• Analyzed amphibian, squamate, and bird tissues from archival collections.
• Included tissues from known liquid nitrogen tank failures as a control.

Main Results:

• Flash-frozen tissues yielded higher DNA quantities but showed significant degradation.
• Peak fragment size and DNA integrity were reduced in flash-frozen samples compared to buffer-fixed samples.
• Degradation in flash-frozen tissues was distinct from catastrophic tank failures, suggesting thaw cycles.

Conclusions:

• Fixative buffers protect DNA from freeze-thaw damage more effectively than flash freezing alone.
• Minimizing freeze-thaw cycles is essential for flash-frozen samples.
• Employing multiple preservation methods enhances DNA protection in field collections.