Genetic Analysis in C. elegans

Lab Instructions #1: Introduction to C. elegans

By the end of this laboratory exercise, you should be able to

manipulate nematode worms using a stereomicroscope and a "worm" pick;
distinguish the two sexes, hermaphrodites and males, and the different stages of the life cycle, particularly the fourth larval stage (L4).
set up a genetic cross between wild-type (N2) hermaphrodites and males. The males will be cultured for later use.

Exercise sterile technique at all times: KEEP THE LIDS ON THE PLATES EXCEPT WHEN TRANSFERRING WORMS.

Obtain the following materials:
1. a plate containing only wild-type (N2) hermaphrodites,
2. a plate containing wild-type (N2) hermaphrodites and males ,
3. a plate seeded with E. coli bacteria, and
4. a worm pick.
Examine the worms closely and attempt to distinguish L4 and adult hermaphrodites, and L4 and adult males. First become familiar with the hermaphrodite stages by examining the plate from 1a; then proceed to identify the males from 1b.
Practice manipulating the nematodes using the dissecting microscope and "worm" pick. Initially practice picking up worms and putting them down on the same plate. Because males may be in short supply and are needed for the crosses, practice with the adult hermaphrodites. Worm manipulation does take practice. Be patient and keep trying!
Once you command sufficient skill to transfer the animals without brutalizing them or the agar surface, proceed with the cross, as follows:
1. Transfer five L4 males to an empty, seeded plate. Using a pick full of "sticky" bacteria, remove contaminating eggs and larvae which were inadvertently transferred and dispose by flaming.
2. Seek verification that the proper animals were selected.
3. Transfer two L4 hermaphrodites to this plate. Be sure to remove unwanted animals which tagged along.
4. Again, seek verification that the proper animals were selected.
5. Properly label your plates with your initials and indicate the animals crossed.
6. Place plates in the appropriate incubator.

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Genetic Analysis in C. elegans

Last Updated: Sept. 10, 1997