Originally posted on WormAtlas by “Caenorhabditis elegans”, May 24, 2004
How do different genotypic strains like N2 compare to osm-10, and if so, is their anatomy different? I know that dumpy is different, but I don’t know if all genotypes have a different anatomy?
Originally posted on WormAtlas by “hall”, May 24, 2004
No, not all mutant strains show any visible difference, and many phenotypes that can be detected by electron microscopy are virtually invisible by light microscopy.
The mutation osm-10 was first isolated by a distinctive change in the live mutant adult’s behavior when placed on an “osmotic gradient” test plate. So their behavior, their movement pattern, is unusual - but only when tested in a specific assay, probably not in spontaneous behavior on a normal culture plate.
But to my knowledge, osm-10 animals do not show any structural change in anatomy noticeable at the light microscope. I do not know if anyone has yet looked closely at this mutant with the electron microscope? Perhaps someone else can say. Some osm mutants are known to show physical changes in sensory anatomy when viewed under the electron microscope. See the HTML copy of the Perkins et al paper on the front page of the WormAtlas website (listed as item #7) for an example of such changes.
David Hall
Hello,
I’m another newbie (to the list and, to some extent, to C. elegans). I registered to ask a very similar question. I’d like to develop a second year Genetics lab (one afternoon, not a whole course) that allows the students to observe phenotypic consequences of known gene mutations. We’ve got N2 and dumpy5 worms. Are there many more? I’m sure we could set it up so that behavioural as well as morphological mutations could be examined Any suggestions? We’ll probably do flies too, but worms are much easier to control!
Thanks,
John Taylor
University of Victoria
British Columbia, Canada
Hi John -
First off, a single afternoon lab presents some challenges. Worm manipulation is a rather delicate skill not easily learned in such a short time. So I’d suggest that the lab just be based on scoring mutants.
Regarding mutants, here are a few quick recommendations. There are many more that would be worthwhile.
unc-22 (Titin homolog; twitcher phenotype; perhaps the most often isolated gene in genetic screens)
rol-6 (collagen; roller phenotype; people freak out when they first see this, it’s a must)
sma-3 (SMAD; animals are smaller than wildtype)
lon-1 (animals are longer than wildtype)
You might also look at some of the triply marked mapping strains such as EG1000 and EG1020. Each chromosome is independently marked with visually distinct markers. You can create heterozygous animals with these to demonstrate segregation.
Personally, I think I might stay away from the behavioral mutants. They can be difficult to score to the untrained eye.
Regarding the experiment:
One approach that you might take is to stage a series of crosses in advance such that you can have P0s, F1s, and F2s from a given set of crosses all ready on the same day. For example, 6 or 9 days prior to the lab you start the crosses. 3 days later, you collect F1s and set up more crosses. 3 days later you pick F2s from the first set of crosses, F1s from the second set, and set up one final set.
On the day of the lab, students begin by examing plates of P0s. Then you give them a plate of F1s as if they themselves had done the picks and they are now looking at the next generation. And so on for the F2s. Using such a strategy, you can explore lots of cool things: independent segregation, epistasis, etc. It’s not as confusing as it sounds to students and it is an efficient use of time. It’s also not as cool as picking wild type heterozygous F1s and seeing all sorts of crazy mutants coming out in the F2.
You can also do things like spiking wild type populations with mutants. I think the thrill of the hunt is a little more interesting to students than just looking at individual plates of isogenic animals.
(We should probably start a separate “Teaching Resources” section of the forum…)
In addition to Todd’s suggestions, some of my favorites for demonstration purposes are:
lin-15(n309), Multivulva, bumps on ventral surface
unc-32(e189), coiler Unc
let-23(sy1), Vulvaless “Bag-of-Worms”
Oh yes, how could I forget the bag of worms! That’s a terrible oversight on my part.
I know that the original question wanted information about a one day laboratory experience using the nematode. But teachers looking for ideas in this realm should also take a look at the website www.wormclassroom.org
This website is designed to share ideas and course materials along several avenues, including developmental biology, genetics and neuroscience. Most is aimed at the college level, but I expect that much can be adapted to the high school level as well. Definitely a good place for teaching ideas and sharing.
And don’t be afraid to look for those pesky behavioral mutants. Features like egg-laying and defecation involve periodic motions that are easily quantified and subject to mutation. Sensory mutants can be interesting to probe, whether it involves touch, taste or temperature, and simple screens are well described to separate them out.
It’s useful to separate genotype, phenotype, and anatomy here. A mutation can produce a clear morphological phenotype, alter behavior or physiology, or have no obvious appearance under routine light microscopy. N2 versus osm-10 is a good illustration of why the assay matters: a strain may differ functionally without showing an obvious structural change. For a teaching lab, I’d record strain, genotype, observed morphology, movement, and assay conditions separately so subtle differences aren’t mistaken for anatomical ones. A 96 Well Plate Template at:96wellplatetemplate.com can also help organize strain-by-strain observations when running multiple assays or replicates, especially when several mutant lines are being compared.