====== DNA samples ======

Lifelines has extracted DNA from the blood of many of our participants (the total number of DNA samples currently exceeds 160,000, and our library of DNA samples continues to expand as we perform DNA extractions on a weekly basis).

===== Facilities =====

To minimise the risk of outside contaminants, there is a dedicated space for DNA processing at our laboratory. DNA processing is kept completely separated by means of an airlock, and the DNA facilities are constantly kept at a positive air pressure in comparison to the other facilities.

===== Extraction Methods =====

Lifelines made use of the Qiagen Autopure LS until 2018 to perform inorganic DNA extraction of packed cells((defined as all of the material that remains after the plasma layer has been removed from a BD Vacutainer® 10.0 mL K2E (EDTA) 18.0mg Plus blood collection tube (or equivalent).)). As of January 2018 Lifelines has transitioned into using the Perkin-Elmer Chemagic 360 to perform magnetic bead DNA extractions on the buffycoat layer of a BD Vacutainer® 10.0 mL K2E (EDTA) 18.0mg Plus blood collection tube (or equivalent).

===== Quantity & Quality =====

Lifelines uses UV-Vis spectroscopy to determine nucleic acid concentrations and -purity (as assessed by the A260/280 and A260/230 ratios) on the ThermoScientific NanoDrop-8000 platform and/or the Trinean DropSense96 platform.\\

Lifelines has historically considered the following fit for classification as "pure" DNA, although this is currently pending review.\\
  * Concentrations: >20 ng/μl((DNA concentrations <100 ng/μl and >1500 ng/μl are verified by repeat measurements, at diluted concentrations if required))
  * A260/280: 1,69 – 2,01\\
  * A260/230: 1,49 – 2,51\\

===== Sample Storage =====

After DNA quantity and quality has been ascertained, the DNA samples are moved into long term storage at -80 degrees Celsius. In order to minimise the effects of repeated freeze-thaw cycles on the DNA, Lifelines also maintains a collection of normalised (100 ng/μl) DNA samples stored at 4 degrees Celsius.