The small scale Mad Scientist in me is looking to create a master race of Superflies. Would it be possible to spray a diluted form of “Raid” (or whatever is commonly used to get rid of them) into a holding tank full of fruit flies, wait two weeks, repeat with higher doses, and eventually get a line of flies immune to Raid? If yes, Muuuhaaaahaaaahaaaaahaaaaa.
Have fun, just make sure you’ve produced all the kids you care to have because powerful oganofluorine pesticides are not all that respectful of species boundaries.
11 ounces. Cyfluthrin and rel. comp 2.15%
Why not breed them based on both size and intelligence? Then after a while on vocal ability. Imagine how popular you’d be with the chicks, walking around with a talking fly sitting on your shoulder like a parrot!
<Eyebrows furrowed, fingers steepled ala C.M. Burns> Excccellennnnt
You probably could produce a fruit fly that would excel in one or two characteristics. However I think we are seriously lacking in our knowledge of what constitutes a fruit fly with superior survivability and fecundity in a variety of environments.
For example, we can breed thoroughbred horses that can run really fast. However, they tend to have other problems that require a lot of care. That doesn’t matter because in the thoroughbred’s environment that care is provided. Left out in the wild, the thoroughbred would dissapear and be replaced by something like the mustang.
And those who can’t spell should also disappear.
I actually work with Drosophila, so I suppose I’ll field this one. Selective breeding for one trait is called a genetic screen. Nowadays, we mutagenize (X-rays, gamma-rays, transposons, or methane ethylsulfonate usually) and look for our phenotype in the progeny. This is far faster than depending on naturally present genetic variation in wild type populations (which is what you are suggesting). We often have to do quite a bit of genetics to isolate and map the mutations created. I have done my fair share of screening and can say it is truly a pain in the butt.
Screens have been done for almost any trait imaginable in fruit flies. This includes organophosphate resistance, size, and intelligence. Genes have been found which are correlated with each of these. We have big flies, small flies, smart flies, dumb flies, and flies which aren’t killed by regular pesticides already.
There are a number of problems, however. I don’t know if anyone has carefully assessed this, but my suspicion is that genetic screens always lead to flies which are less fit than wild type populations. Even if you genetically engineer (reinsert overexpressing detoxification genes) pesticide resistant flies, chances are that your overexpression construct will have some toxic effects that are worse off for the fly in the wild than being resistant to pesticides. The same is true of mutations you would create in a standard genetic screen. You end up with a fly with whatever one phenotype you are selecting, but those flies are less healthy out in the wild.
This is based on the simple fact that nature and evolution selects in a multifactorial, complex fashion. In a screen, we select based on one trait. Evolution selects on all of the traits. If it were advantageous for a fly to have a bigger size, more intelligence, or pesticide resistance, it would be done by evolution. Selection wouldn’t be placed on one or two genes, but on all of the genes. This is not something that would be easy to accomplish in a controlled scientific setting, or even something that would be easy to evaluate scientifically (although in today’s post-genomic era, we are getting closer…)
A group of Drosophila got involved in a radical political movement in the 1930’s-40’s, & tried this very thing.
They were the Gnatzis.
Bosda I remember them - their symbol was a Black Flag.
edwino I would have thought that pressure selecting the flies by “Raiding” a big batch of them and allowing the survivors to reproduce would be more efficent than forcing mutations and hoping for the best. It doesn’t seem like your taking advantage of the fruit flies fast generation cycle via the latter.
A few things. First, remember that evolution does nothing to create the mutations. Imparting a selection acts on the natural variation in the population, enriching alleles already around. Only mutagenesis will create new alleles. In order to do your method, you will have to start with a large, genetically diverse group of flies and hope that there is enough appropriate polymorphisms in the population to give pesticide resistance. Sure, new novel mutations will crop up from generation to generation, but this is so slow as to be negligible over any reasonable amount of time. Fruit flies have a short generation time, but it is still 10 days from progeny to progeny at fastest. So be prepared to deal with a huge population. I will point out that there will be a bunch of technical problems (drug delivery, dose response, separating progeny, isolating mutations or establishing true breeding lines, etc.) that will make your life hellish.
We mutagenize to create new mutations instead of depending on the genetic variation in a population. Instead, it is better for us to start with the most homogenous population available, because it is easier to pick out new mutations from a plain genetic background. If one can do this, one can establish true-breeding lines. Your way would create a population with an enrichment of pesticide-resistance alleles. What would happen is without constant selection, these alleles (which by themselves usually have negative fitness) would breed themselves out of the population due to recombination and independent assortment. My way would create true-breeding lines. If the population were only to mate with one another, the alleles would never be lost even if there was significant negative fitness involved.
Either way, you end up with a population that is less fit than wild type unless it is under constant selection. If you don’t restrict breeding, you will quickly lose the mutations. Since you are talking about releasing your superflies upon the unsuspecting masses, this implies that you would not be able to keep selection present and maintain breeding. All advantages that you had bred into the flies would quickly be lost.
Okay, ** edwino ** I just finished genetics with lots and lots of Drosophila so I gotta ask, how do you test a fly’s intelligence? Most of the ones seemed fairly dense, incapable of flying from one bottle to another in timely freaking fashion, that sort of thing. Maybe they were just high on flynap…
First off, I’m not REALLY thinking of doing this.
Curious, what is your most successful mutation method and how successful is it? What kind of percentage of nonlethal mutations can you get out of a given population? Also, how do you know what you’ve got? How do you figure out how the mutation will express itself?
Not thinking of doing it? Not thinking of doing it? Yer kidding me… I thought I had found another potential recruit for my burgeoning Graduate School of Evil Biomedical Sciences. Oh well. Anyway, no Evil Scientist worth his salt works with fruit flies. They just aren’t that much of a nuisance. Use locusts, moths, or medflies for real economic damage. Or, if you need a gimmick, use scorpions, cockroaches, goliath beetles, tarantulas, or praying mantises.
Anyway, to continue.
There are a number of intelligence tests in flies. The one that I am most familiar is called the T-tube, to assess memory. Flies are put into the barrel (the bottom of the T), and are allowed to fly into one of the arms. In each arm, there is a neutral scent. A shock is administered in one arm, and the flies grow to associate the smell with the shock. One can test how long this association takes, how long it is retained, and all types of other things. There are mutants which affect all types of different things which have been discovered through T-tube screens.
There are different mutation methods that give different results for creating your mutant army. The three I am most familiar with are transposable elements called P-elements, a chemical mutagen called methane ethylsulfonate (EMS), and X-rays. P-elements are wonderful at creating insertional mutations, but they do not saturate (they only incorporate in about 70% of genes, usually right at the beginning of the gene). EMS is good at causing point mutations and small deletions. Off the top of my head, I remember that 25 mM EMS causes around 12-20 mutations in each F[sub]1[/sub] fly (we feed the father flies the EMS, and it mutates their sperm). More than this is an issue – it becomes hard to separate out individual mutations and the mutagenized males become sterile. X- and gamma rays are good for causing small to large deletions and chromosomal rearrangements (like inversions). Usual dose is on the order of 4000 rads, and I assume that it would give also around 12-20 mutations (3-4 mutations per chromosome arm).
Mapping the mutations is a big, big problem in genetics – this is called positional cloning and can easily take a year even in the fruit fly, which is probably the easiest multicellular organisms with which to work. Mice people can spend a PhD on it. Human people can make a career out of it. First, one has to recover and score a mutant, which can be very difficult. For instance, if you are looking for a recessive lethal mutation, it can sometimes take 3 generations after mutagenesis (and F[sub]3[/sub] screen) just to identify the mutation. This, needless to say, is incredibly painful. So, once the mutation is recovered, we first map it to a chromosome. This is easy in flies because there are only 4 chromosomes. This is a fairly basic thing to do in fly biology (involving balancer chromosomes and their dominant markers, employing Mendel’s law of independent segregation). Then we meiotically map the mutation with recombination to a marker chromosome, which allows us to place it in a gene neighborhood (using genetic linkage mapping and Mendel’s law of independent assortment). Then, we look for candidate genes and begin molecular and genetic studies to put our mutation in a particular gene. These are things like Southern blotting with RFLPs, fine deficiency mapping, complementation analysis, candidate gene sequencing, and SSCP/heteroduplex analysis. Fun, exciting.
Thanks edwino. I had no idea that mutation could be so “dependable.”
Slightly off topic: Edwino, a few months earlier you mentioned that you had worked on a paper regarding fruit flies with some very interesting results, that might get published in a major magazine. What was it about?
Thanks, ** edwino, ** like I said, I’m afraid the ones I worked with would have failed miserably.
Check back at the beginning of next year. I’m still working. Science is slow, especially when it doesn’t work the first time. Thanks for remembering, though… It is really quite an ego boost to know that people read and remember what you say around here…
You have to remember that even our “wild type” flies have been kept in small populations in laboratories for so long (approaching 100 years for some of them), that they are by this point completely inbred and stupid. This is even more pronounced in mice. In order to get a constant genetic background, one constructs an inbred strain. Take two siblings and mate them, then take one male and female offsping and mate them. Repeat for 20 to 40 generations. The intelligence tests they use on lab mice (Rota-rod and water maze come to mind) don’t work on real wild mice – put a wild mouse in that thing and it is up out of the test and into the walls before you can blink an eye. We need it for genetics, but it makes it difficult to characterize suspected brain functioning mutations because the mice are already so low-functioning to start with.