Decisions have been made, orders have been placed, and materials have arrived. It turns out that we are treading a relatively well-worn path of DNA bar-coding. The goal for the semester is to extract, amplify and sequence the rbcL gene for the candidate food plants and the chloroplasts maintained by the slugs. Because rbcL encodes a component of the photosynthetic complex of the chloroplast, and the gene is found in the genome of the chloroplast (rather than the nucleus of the plant), the origin of the chloroplasts that the slugs are carrying can be identified on the basis of the sequence of the gene. Fortunately for us, the sequence of the rbcL gene has been studied by a lot of people. The chloroplasts of all plants have it, but it varies a little from one species to another. That variation can be used to examine how closely related different species are, or to determine if two populations that resemble one another are actually different species. Each species has a unique sequence or “bar code,” that can be used to identify it, and to distinguish it from other species.
Therefore, much of the work has been done for us. Kits, such as the one in the above photo, are readily available, procedures are largely worked out for amplifying the amount of DNA using polymerase chain reaction (although the primers for these algae may be a little tricky), and there are companies such as GeneWiz that provide a relatively inexpensive and simple resource for sequencing the resulting DNA. Makes a nice change after a career spent soldering and tweaking in order to perform experiments using arcane methods.
On your next visit, you may find a photo of DNA bands on an agarose gel. Or maybe something else.