8/10/2019 C. Elegans Lab

1/2

C. Elegans Lab

Austin Cao, AP Biology

2/27/14

Section 1: Overview

C. Elegans is a species of roundworm commonly found in temperate soil environments.

Because they are transparent, studying cells is a lot easier. Researchers have looked at cell

functions like meiosis and apoptosis in C. Elegans to gain a better understanding of how

these processes happen in human cells. Specially, we have mapped the development of all

of their somatic cells and studied their asymmetric cell devision. The genome was the first

multicellular one to be sequence, in 2002. It includes 6 chromosomes, and 100 million

base pairs.

Section 2: Lab observations

What do the E. coli OP50-pBAD lawns look like?

Largely continuous, with small external groups

light brown/white

translucent

covers 1/3 plate

Record observations about the C. elegans strains.

400-600 worms per plate

1/3 E. coli on plate

half were in the larval stage

no eggs were seen mutant and wild-type looked the same

Section 3: Statistical analysis

NaCL side Control sideWild-type 13 2Mutant 0 0

8/10/2019 C. Elegans Lab

2/2

chemotaxis index = (# NaCl - # control)/ (# NaCl + # control)

chemo for wild-type C. elegans = .73

chemo for mutant C. elegans = undefined, 0

The section explains that outliers affect the final chemotaxis calculation dramatically. Because oursample size was relatively small, this is especially true. A larger population is tougher to count but

gives more accurate results (less likely to skew because of outlier).

Section 4: Focus questions

In what way are the solutions placed at the NaCl and the Control spots on the assay agar plate

similar or different?

All factors are the same except for the fact that the C. elegans have been trained to seek

out NaCl for E. coli. Theres no actual difference other than the neutral stimulant.

Is daf-18 an essential gene for C. elegans survival? Explain.

Daf-18 allows for associative learning behavior, so it is likely that this trait is required for

C. elegans to know where to get food, and to survive. Perhaps mutants can survive in lab,

but they have a decreased survival in nature.

What is the benefit of having a functional daf-18 gene in C. elegans?

Daf-18 helps C. elegans learn things in their lifetime. Knowing where to get food with a

symbol or marker is useful and more efficient.

Why are NGM Lit agar plates not used for the chemotaxis assay?

Only the NaCl should be used by the C. elegans as an association with E. coli.

What would happen during the chemotaxis assay if C. elegans were starved rather than fed prior

to the chemotaxis assay?

Results would be reversed.

Design an experiment to test this hypothesis.

Repeat experiment in exactly the same manner, except do not feed the C. elegans whenexposed to the NaCl.