This will be my first post on this blog. I hope it won't be my last. I will sidestep the introductory post and jump right into it--the only purpose of this will be to educate myself and improve my writing, in a more structured way.
I've just started my first year of graduate school. My first exposure to science was about seven years ago. I'm amazed at the changes that have happened in that time. Classical genetic techniques seem to be anachronistic. The blunt tools that were so elegantly wielded to produce precise results are now cast aside for the sharp, more precise tools that can be used bluntly to produce comparable, or even better, data. In a way, science is less beautiful... It should be our aspiration, as young scientists, to be as clever as our predecessors were. Combine, modify, tinker.
Although people seem to think fishing expeditions are a recently employed phenomenon, this is just not true. A classic example of a fishing expedition, used in the early days of fly genetics, is the topic of the post today. I was previously NOT familiar with this technique, so I will try to not mess up too much. What follows is my understanding of enhancer traps:
Simply put, enhancer traps are a way to detect novel genes.
Before the day of high-throughput sequencing, the genome sequence of the model organisms that people worked with weren't known. gasp. In fact, no one could even say how many genes there actually were. By sticking random pieces of reporter genes (e.g. fly eye color/GFP expresion) into the DNA, and hoping it got put near an enhancer, novel genes could be mapped.
Two questions come to mind:
1) how do you stick the reporter in front of an enhancer?
2) how do you determine what gene the enhancer trap corresponds to?
The answer to the first comes from the use of a transposable element, called a P-element. Explaining exactly what this element is, and the phenotype it confers is not my goal here, so I won't go into it. But WIKI does have a pretty nice summary about them. Just have it be known that they used a version of this transposon that would not jump after a single insertion.
2 things about P-elements that make them ideal for this assay are:
1) They have a weak promoter (so they NEED a nearby enhancer to allow for transcription of genes)
2) They may hijack enhancers so they no longer function for the gene(s) they are supposed to regulate (or they could insert in the middle of a gene and kill it that way)
These two factors combine to give a visual readout (e.g. eye color/GFP) and a functional readout (disruption of gene(s)).
After you get an insert that has a function, you can map where the insert is (because you know that sequence), and therefore approximately map what gene you're interested in.
I've left out details, but I think this short post, along with some decent googling, will allow anyone to figure this topic out as well.
Ciao,
-TSD
