[Week 4: Feb. 24-28] Nematodes

I've mentioned C. elegans several times, so I haven't talked about them in detail yet. 

Here's a picture I took with my phone through the microscope

So, what's a C. elegans? Here we go: 

Caenorhabditis elegans is a type of nematode that's about 1 mm long as an adult. It's a free-living (not parasitic)  hemaphroditic roundworm that's normally found in soil where it eats microorganisms such as some bacteria. 

Why do people use them in labs?  

• Similarity to other organisms
• Eukaryotic, useful as a model to see how other multicellular organisms (like humans) work
• Depending on your bioinformatics method of assessment, 60-80% of C. elegans genes are homologues with human genes.
• Simplicity
• Adults have >1000 cells, but their tissues are well defined and have been studied extensively
• They have a relatively small genome and it's been sequenced completely (9.7 * 10^7 base pairs, by comparison, the human genome has 3 * 10^9 base pairs)
• Since there're so small, there's not much anatomic variation between individuals. They're eutleic, so all of them have the same number of cells. Their neurons are also eutelic so scientists can reconstruct their nervous systems and study them.  
• They're transparent so you easily see dyes if you're tracing something and you can see individuals in different stages in life which is really important for identifying L4s. L4 individuals are also called "virgins" and are useful in crosses and making strains of nematodes.

L4s have a clear spot in the middle of their bodies. It looks kind of like an eye here.
This is from a book called The Nematode Caenorhabditis elegans

• Their biology
• You can easily grow them on petri dishes with agar with a bacterial lawn of E. coli. 
• You can freeze their eggs for decades and healthy individuals will hatch so you can store strains for over thirty years 
• They have brief life cycles: 2-3 days/ generation.
• You can study genes using RNAi (RNA Interference) to your advantage. When the worm encounters a double-stranded RNA segment that corresponds to one of its own genes, it treat it like a virus and down-regulates its gene so you can control gene inhibition which can be useful if you're studying the effects of different genes. 

That's all for now.

If you're curious for more feel free to ask. Here're my sources:

• Kaletta, Titus and Hengartner, Michael O. (2006). Finding function in novel targets: C. elegans as a model organism. Nature Reviews Drug Discovery, 5, 387-399
• Waksman Student Scholar. (2000). C. elegans as a Model System. Retrieved from the Waksman Institute of Biology of the University of the State of New Jersey website: http://avery.rutgers.edu/WSSP/StudentScholars/project/introduction/worms.html
• Wood, William B. (Ed). (1988). The Nematode Caenorhabditis elegans. Long Island, NY: Cold Spring Harbor Library Press 

P.S. This wasn't one of my sources, but I stumbled across this website if you're curious to know more. 

• Worm Atlas. (2006). INTRODUCTION TO C. elegans ANATOMY. Retrieved from http://www.wormatlas.org/ver1/handbook/anatomyintro/anatomyintro.htm