This is the fourth post in a five-part series on Arctic flora research at the Canadian Museum of Nature. Join us as museum researcher Paul Sokoloff introduces the fieldwork and lab work involved in writing a new flora of the North American Arctic.
DNA (deoxyribonucleic acid—I promise I won’t test you on that) is pretty prominent on the cultural radar these days. From forensic television shows to debates on genetically modified organisms, most people are familiar with the concept of DNA as the blueprint of life.
Therefore, when I mention to people that I work in the DNA laboratory at the Canadian Museum of Nature, they ask me if I’m using DNA to solve crimes or to create new species. Fortunately, most people aren’t disappointed when I tell them no, we aren’t catching criminals or performing mad science. Rather, we sequence the DNA of organisms to better understand their evolutionary relationships—this is called systematics, as I mentioned in my last post.
A commonly used analogy for the DNA molecule is a spiral staircase, because if you could shrink yourself down to the size of molecules, you’d see it looks like one! However, I think a better functional metaphor is a vinyl record. Just as a record holds a song as a series of bumps in a groove, DNA holds all the information necessary for life encoded as a series of molecules.
On a turntable, the record player’s needle travels through the groove and interprets the bumps as sounds. Within a cell, proteins unzip the double-stranded DNA molecule, and interpret the DNA sequence as instructions for building more proteins. These proteins carry out the basic functions of the organism.
Some portions of the DNA provide the code for these protein sequences—like the music tracks on a record, while much of the molecule does not code for proteins (called non-coding DNA)—like the silent spaces between the songs. DNA, in both these coding and non-coding forms, accumulates mutations through time. Consequently, the genomes of species often differ enough to allow them to be differentiated on the basis of differences in their DNA sequence alone.
This all means that the fairly recent innovation of (relatively) cheap DNA sequencing has opened up powerful new tools for systematics. By extracting the DNA from plant and animal cells, and running it through a machine capable of reading the chemical sequence of a specifically targeted DNA molecule, we can generate very large datasets for comparing the evolutionary histories of the organisms we study. In conjunction with the morphological data from the organism, we can refine and re-evaluate our classification of the species.
In the context of our museum’s Artic Flora of Canada and Alaska project, application of DNA tools has not only proven invaluable in confirming the identity of plants collected in the field (often we can re-evaluate the herbarium specimen in light of the DNA data), but also ensures that the names applied to morphologically defined species and groups of species actually refer to natural, evolutionarily distinct groups.
While DNA sequencing cannot replace the taxonomic information contained in the morphology of an organism, it certainly is a powerful addition the systematics toolbox at the museum.