The Power of Comparison

It's always a little awkward to describe what it is I do to people I meet, or people that I'm related to.  Sometimes, when I'm feeling brave (or when I just want to stump someone because I don't want to talk about it), I say I have a Ph.D. in Molecular Evolution, studying the evolution of single copy genes in flowering plants (or angiosperms) if I'm feeling particularly crabby.  It is a guarantee that the conversation will end.

Let's see if I can actually explain the basics of my interests without putting you to sleep or you walking away with the thought that I work in cloning (somehow this is how my parents described what I did to countless people throughout undergrad, I'm not even sure how they would describe it now, but then again, now they can just tell people I'm a stay at home mom).

At the very core of it, molecular evolution is generally the study of how genetic material changes over time.  Usually, studies of molecular evolution are based on DNA sequences - long strings of A/T/G/C - the four nucleotide components of DNA.  You can retrieve some basic information from a single DNA sequence - such as the amino acid sequence of the protein it encodes (if it's a gene), but the greatest amount of information is obtained when you can compare one DNA sequence to another that represent DNA sequences that have a common ancestor (imagine a fork in the road - the two sequences are the two different paths and the single path represents the common ancestor).  When you start comparing related sequences (aka homologous DNA) across different species, then you're in the realm of comparative genomics, utilizing the tools developed to understand molecular evolution.

Remember those compare and contrast essays you had to do in high school English?  By comparing and contrasting sequences, you can identify commonalities and differences at the genetic level that might relate to commonalities and differences at the physical/behavioral level.  You can also use this information to figure out how organisms are related to each other.

Why is this useful? Well, I'll talk about a project that first led me down the path into studying molecular evolution.  There are nematodes (small, worm-like creatures) that chew on banana roots, causing agricultural damage.  Well in some of these nematodes (about 50 years ago) a mutation occurred that meant they would now attack citrus roots.  The banana attacking nematodes were common, but the citrus attacking ones were rare.  But to prevent the spread of the citrus attacking nematodes, rootstock containing the banana attacking or citrus attacking nematodes couldn't be transported to new citrus growing regions since they both looked alike.  We were trying to identify genetic markers to be able to ID the citrus parasitic nematodes, so you could tell them apart. I never reached that endpoint, but we were using comparisons of rudimentary genetic assays to try to identify markers.  I was also able to use those comparisons to investigate how these nematodes were related to each other and from what population the citrus parasitic nematodes likely evolved from.

So yeah, my scientific life is comprised of really complicated ways to compare and contrast - and it's pretty cool what we can figure out doing just that.