Worms Can Feel Touch!
State of Florida: Next Generation Sunshine State Standards
• SC.912.L.16.4 Explain how mutations in the DNA sequence may or may not result in phenotypic
change. Explain how mutations in gametes may result in phenotypic changes in offspring.
• SC.912.L.16.5 Explain the basic processes of transcription and translation, and how they result in
the expression of genes.
• SC.912.L.16.10 Evaluate the impact of biotechnology on the individual, society and the
environment, including medical and ethical issues.
• SC.912.L.14.21 Describe the anatomy, histology, and physiology of the central and peripheral
nervous systems and name the major divisions of the nervous system.
SC.912.L.16.12
Describe how basic DNA technology (restriction digestion by endonucleases, gel
•
electrophoresis, polymerase chain reaction, ligation, and transformation) is used to construct
recombinant DNA molecules (DNA cloning).
Duration: One 105-minute class period
Teacher Prep:
1. Prepare 6 cm agar plates with E. coli (worm food).
• 4-7 days before lab, grow OP-50 E. coli strain in LB liquid broth overnight at 37oC
• 3 days prior to lab pour 6 cm plates. Fill plates with 10 mL of molten agar. Let sit 24
hours to solidify (plates are good for as long as 2 weeks after pouring at room temp
and 1-3 months after pouring if refrigerated).
• 2 days prior to lab inoculate the center of each plate with E. coli.
2. Each student group will need 2 inoculated plates, but having a few extras in case of
unexpected accidents are a good idea. Each plate will contain 3 worms.
3. Label plates by assigning only a letter to represent each type of C. elegans, so the students
are evaluating samples in an unbiased/blind fashion. For example:
• Label A = wild type (touch sensitive)
• Label B = mutant (touch insensitive)
4. 30 minutes* prior to lab, place 3 of each type of worm on plates A, and B. For example:
• Place 3 wild types on A
• Place 3 mutants on B
5. Setup dissecting microscopes for each group 1-24hr
prior to experiment.
*Worms can be plated in the morning and used throughout the day for each class period.
Acknowledgements:
•
Modified from Brain U at http://brainu.org/c-elegans-and-alcohol
©2000-2011 BrainU, University of Minnesota Department of Neuroscience in collaboration with the National Center
for Research Resources, a part of the National Institutes of Health.
•
Modified from Gustavus Aldophus College Resources for Teachers
https://gustavus.edu/events/nobelconference/2011/teachers/files/UnderstandingtheUnc.pdf Gustavus/Howard Hughes
Medical Institute Outreach Program 2011-2012 Curriculum Materials.
What is Caenorhabditis elegans and why work on it?
Image adapted from wormbook.org
What is C. elegans?
C. elegans is a nematode, and a member of the phylum Nematoda. The Nematoda include
roundworms and threadworms, which are smooth-skinned, unsegmented worms with a long
cylindrical body shape tapered at the ends. This phylum includes free-living and parasitic
animals, as well as aquatic and terrestrial organisms.
(Academic Press Dictionary of Science and Technology)
C. elegans is small, growing to about 1mm in length by adulthood, and lives in the soil –
especially rotting vegetation – in many parts of the world where it survives by feeding on
microbes such as bacteria.
A brief description of C. elegans
C. elegans is a non-parasitic, free-living nematode. There are two sexes: a self-fertilizing
hermaphrodite and a male. The adult essentially comprises a tube, the exterior cuticle,
containing two smaller tubes, the pharynx and the gut, and the reproductive system. Most of
the volume of the animal is taken up by the reproductive system.
Of the 959 somatic cells of the hermaphrodite some 300 are neurons. Neural structures
include a battery of sense organs in the head that mediate responses to taste, smell,
temperature, and touch – and although C. elegans has no eyes, it might respond slightly to
light. Among other neural structures is an anterior nerve ring with a ventral nerve cord
running back down the body. (There is also a smaller dorsal nerve cord.) There are 81
muscle cells. C. elegans moves by means of four longitudinal bands of muscle paired subdorsally and sub-ventrally. Alternative flexing and relaxation generates dorsal-ventral waves
along the body, propelling the animal along. The development and function of this diploid
organism is encoded by an estimated 17,800 distinct genes.
Adapted from: http://brainu.org/files/is_celegans_1.pdf
©2000-2011 BrainU, University of Minnesota Department of Neuroscience in collaboration with the National Center for Research
Resources, a part of the National Institutes of Health.
Worms can feel touch!
Objectives:
• The student will identify C. elegans mutants that are insensitive to soft touch.
• The student will describe what effect a single point mutation has on C. elegans sense of
touch.
Materials:
• C. elegans
Wild type
o
Mutant; mec-4 (e1611)
o
• Worm pick
• 2 small agar plates with E. coli (worm food)
• Dissecting microscope
• Toothpicks
• Glue
• Eyelash or eyebrow hair
Procedure:
1. Take a toothpick and glue an eyebrow/eyelash hair to the tip. Let dry (see Figure 1).
2. Obtain plates A and B.
3. Place plate A on the dissecting microscope.
4. Observe how the worms move around on plate A.
5. Take the toothpick and touch the worm by stroking the hair across the mid-anterior
region of the body.
Figure 1: Using an eyebrow hair to test soft touch
sensitivity. (A) Positioning and gluing the eyebrow
hair to the toothpick. The thickened black line
indicates the shaft of the hair; the gray area indicates
the location of the glue. (B) Animals should be
touched by stroking the hair across the body at the
positions of the arrows. The six touch receptor
neurons are indicated.
http://www.wormbook.org/chapters/www_behavior/
behavior.html
Image adapted from wormbook.org
6. In the data table, record if the worm responds to touch with the eyelash. A response is
recorded if the worm starts to move when stroked, or if the animal reverses direction
when touched while moving.
Note: take care to touch the animal only with the eyebrow/eyelash and not with the
toothpick itself. As touching with the toothpick will provide harsh touch, whereas the
eyebrow provides soft touch.
7. Repeat steps 5 and 6 for all worms on the plate.
8. Remove plate A from the dissecting microscope.
9. Repeat steps 3-7 using plate B and record data in the table.
10. Caution: Do not leave worms under light for long periods of time.
Data Table
Worm
1
2
3
Average Responses
C. elegans ______________________
C. elegans ______________________
Plate A
Plate B
Response (+/-)
Response (+/-)
Trial 1
Trial 2
Trial 3
Trial 1
Trial 2
Trial 3