Understanding the Uncs!!

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 6cmagar 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 6cm 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.
  1. Each student group will need 3 inoculated plates, but having a few extras in case of unexpected accidents are a good idea. Each plate will contain 3 worms.
  2. 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 (lots of movement)
  • Label B = mild unc (moderate movement)
  • Label C = strong unc (no movement)
  1. 4 hours* prior to lab, place 3 of each type of worm on plates A, B, and C. For example:
  • Place 3 wild types on A
  • Place 3 mild uncs on B
  • Place 3 strong uncs on C
  1. Setup dissecting microscopes for each group 1-24hr

prior to experiment.

*Depending on the time of day the experiment will take place; plates can be prepared 30 minutes to 24 hours prior to the lab. Expect tracks to increase as time increases.

Notes:

  • Holding plates up to the ceiling lights is also helpful to visualize tracks on entire plate. Thus, microscopic and macroscopic observation by students is encouraged.
  • Lightly dropping the plates on the stage of the dissecting scope (while looking through eyepiece to observe reaction) will trigger rapid movement of wild-type animals, a weaker response from mild Unc, and no response from strong Unc.

Acknowledgements:

  • Modified from Brain U at

©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.

  • Modifiedfrom Gustavus Aldophus College Resources for Teachers Hughes Medical Institute Outreach Program 2011-2012 Curriculum Materials.

What is Caenorhabditis elegans and why work on it?

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 sub-dorsally 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:

©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.

Understanding the Uncs!!

Objectives:

  • The student will identify C. elegansmutants with different types of impaired movement.
  • The student will describe what effect a single point mutation has on C. elegans movement.

Materials:

  • C.elegans
  • Wild type; N2 strain
  • Mild unc; unc-42(e270)
  • Strong unc; unc-51 (e369)
  • Three small agar plates with E.Coli (worm food) per group
  • Worm pick
  • Dissecting microscope
  • Sharpie for labeling plates
  • Ruler

Procedure:

  1. Label Plates A, B, and C.
  2. Using a sharpie and ruler, draw 4 quadrants on each plate. Draw a horizontal and vertical line that divides the bacterial lawn into 4 equal parts. Label the quadrants as shown.
  1. Observe how C. elegans move around on the plate using a dissecting microscope. Do not leave under light for long periods of time.
  2. Hold plate up to the light and observe.
  3. Lightly drop the plates on the stage of the dissecting scope while looking through eyepiece to observe reaction.
  4. Draw and label the movement of the worms in the data table. Note differences in the type of movement of the actual worm as well as the patterns on the plate.
  5. List the quadrants that have tracks present in the data table.
  6. Name the worm type on each plate.

Data Table

Plate / Tracks
(Draw the tracks) / Observations
(List three) / Quadrants
(List quadrants with tracks)
C. elegans A
______
______/
C. elegans B
______
______/
C. elegans C
______
______/

Gustavus/Howard Hughes Medical Institute Outreach Program 2011-2012 Curriculum Materials