saliva Samples were collected 13 months ago in OG-500 tubes (genotec) and preserved at room temperature and I started DNA extraction 3 months ago .the end point is to do sanger sequencing for specific mutations . I extracted DNA using Genotec saliva isolation kit according to their protocol. Results were tested with Nanodrop (the curves were perfect ,260/280 around 1.8 with concentration around 200-300 ng/microliter) well that looked great and started PCR with primers and protocol used by a colleague who searched for same genes in different patients.
PCR results were so disappointing apart from 15 patients out of 80?????
I did a gel electrophoreses with 1% gel and GELRED , DNA was degraded with no clear band at all??
DNA should stay stable for years in these tubes??
any suggestions for better DNA quality ??
I suggest you next time should extract the DNA first and keep the DNA at -20 degree celsius. Keeping whole cell samples for months might degrade the genomic DNA.
unfortunately samples were collected from multiple centers and we were not able to isolate DNA till they reached Zurich. These tubes have a special stabilizing fluid which I think should protect the DNA :(
this research published in 2017 compared saliva samples stored up to 12 months and they claim they were able to extract DNA of good quality and quantity
Dear
You should preserve the saliva samples at very low temperature. This will keep the cellular proteins inactive and DAN will be protected for a long time.
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