I’m working on DNA barcoding of two marine fish species. My tissue samples are 1–2 years old, stored in 97% ethanol without changing the alcohol. I used the TIANGEN Blood & Tissue Kit for extraction. Gel showed clear bands, and Nanodrop was fine (~100 ng/µl, 260/280 = 2.0), but sequencing results are poor. Chromatograms are messy and BLAST shows ~80% match to Shewanella baltica.
Could this be due to degradation or contamination from storage? Is there any method to salvage these samples e.g., re-extraction, extra purification, or modified PCR? Would switching to another extraction method help?
Any advice is appreciated.
This looks like contamination of the samples prior to storage. However, even if 80 % of the sample is something else, isn't there still enough of the fish DNA to get meaningful results (ignoring the bacterial contamination)? If the goal is to completely sequence the genomes, you may need to get new samples, though.
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