Facts about the Worm C. elegans:

• First described as a species in 1900
• Proposed as a model organism by Sydney Brenner in 1965
• In the wild: lives in the soil and eats bacteria
• Easy to culture in the lab on plates growing standard E. coli
• Size: 1mm and transparent, so can only be studied with a microscope
• One of the smallest, simplest organisms with a nervous system

Figure 1

• Lifespan:
• Egg (1 day)
• 4 Larval stages with molting after each one (3 days)
• Adult (Lives another 7-10 days)
• Total Lifespan: about 2 weeks
• 2 sexes: self-fertilizing hermaphrodite and male
• Physiology:
• Mouth and Digestive System
• Reproductive System
• Nervous System (but no brain)
• Muscular System
• Cuticle (skin)
• Can sense chemicals (smell and taste), sense of touch, can detect heat but not light or sound

Figure 2

• Genome:
• 6 different chromosomes (humans: 23)
• Genome size 100 million bases (humans: 3 billion)
• About 20 000 genes (humans: 30 000)
• About 6 000 C. elegans genes have human homologues
• Entire genome of C. elegans has been sequenced, and so has that of 4 other similar worms, with another 5-10 on the way
• Laboratory Experiments
• Knock out one gene at a time to see what the effect is
• Insert Green Fluorescent Protein (GFP) into the genome to make parts of the worm turn green
• Feed the worm with bacteria containing Interfering RNA, which will turn off just one gene
• Destroy just one cell during embryogenesis and see what happens

Figure 3

• Bioinformatics Experiments:
• Compare C. elegans genome to that of other worms to look for regions of sequence that are conserved (shared) and might be important
• Measure the gene expression of a specific cell or tissue and see which genes are being used
• Nobel Prizes have been awarded to 5 C. elegans researchers:
• 2002 Nobel Prize in Physiology or Medicine
• Sydney Brenner – pioneering genetic studies
• John Sulston – elucidating the exact cell lineage from one fertilized egg to 959 cells in the adult
• Robert Horvitz – investigation of programmed cell death, which later turned out to be very important in the development of cancer
• 2006 Nobel Prize in Physiology or Medicine
• Andrew Fire and Craig Mello– discovery of RNA interference during translation