WHAT IS eDNA?

Focus-Science and Technology - - BIOLOGY -

DNA ex­tracted from an or­gan­ism can re­veal a great deal about its re­lat­ed­ness to other liv­ing things, both in the small-scale sense of how it com­pares with other pop­u­la­tions within its species, and in the broader sense of where it fits within the tree of life.

But if it only takes a tiny sam­ple of or­ganic tis­sue – a sin­gle skin or gut cell, for ex­am­ple – for DNA to be ex­tracted, then could DNAre­trieval tech­niques be so­phis­ti­cated enough for us to col­lect DNA that liv­ing things leave in their en­vi­ron­ments, via their shed cells, urine and fae­ces? The an­swer is yes. In a se­ries of stud­ies that first ap­peared in print dur­ing the 1990s, ecol­o­gists and ge­neti­cists world­wide have shown how the pres­ence and iden­tity of or­gan­isms in an area can be ex­tracted from soil, ground­wa­ter, ice, fresh­wa­ter and sea­wa­ter via so-called en­vi­ron­men­tal DNA or eDNA.

By col­lect­ing water from Loch Ness, sci­en­tist Prof Neil Gem­mell and his team hope that they have ob­tained eDNA from the loch en­vi­ron­ment. They have also taken sam­ples from nearby lochs to an­a­lyse their eDNA too. Back in the lab­o­ra­tory, the sam­ples will be an­a­lysed, and any eDNA will be iden­ti­fied and ex­tracted. The sam­ples are then pro­filed and com­pared to those al­ready in ge­netic data­banks. Many species al­ready known to be present in the loch will be iden­ti­fied in this way. The hope is that species new to the area, and per­haps even new to sci­ence, will be dis­cov­ered as well.

RIGHT: Most eDNA found so far be­longs to liv­ing species al­ready known to sci­ence. How­ever, some eDNA has been found from ex­tinct an­i­mals, like mam­moths and gi­ant sloths. This proves that eDNA can last for thou­sands of years in the right con­di­tions

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