C. elegans
Goals
•
Learn how to work with a common model
organism
•
Observe actual scientific worm crosses
•
Learn about common genetic principles through
these crosses
Basic C. elegans Information
• First used as a model organism by Sydney Brenner in 1965
• Is a nematode or roundworm. Adult are around 1mm in
length
• Found in the soil
• Feed on E. coli
• Transparent body
• Relatively quick life cycle, ~3 days from egg to mature adult
• Large progeny number, ~240 eggs
• Vast number of easily identifiable phenotypes
• Completely sequenced genome - 100 million base pairs which
make up 20,000 genes
Body Structure
• C. Elegans is a multicellular eukaryotic organism which has a
simple body structure.
• There 959 cells in the adult hermaphrodite and 1031 cells in
adult males.
• The developmental fate of every single one of these cells
has been mapped out.
• C. elegans has many of the same organ systems as other
animals. It contains a digestive, muscular, nervous, and
reproductive system.
• C. elegans is one of the simplest organisms with a nervous
system. In the hermaphrodite worm the nervous system is
composed of 302 neurons whose pattern of connectivity has
been completely mapped out.
C. Elegans Body Structure
C. Elegans Sex differentiation
• The C. elegans population is made up of hermaphrodites
and males.
• Hermaphrodites
reproduce sexually
• Males are less
prevalent in the
population (0.05%)
and arise at a
frequency of about
one in several
thousand individuals
Sex Differentiation
Hermaphrodite Worm
Male Worm
Genetics
• C. elegans has five pairs of autosomes (non-sex
chromosomes) and one pair of sex chromosomes
• Sex in C. elegans is based on an X0 sex-determination
system
• Hermaphrodites have two sex chromosomes (XX)
• Males have one sex chromosome (X0)
C. Elegans Life-Cycle
• At 20C the
laboratory strain of
C. elegans has an
average life span of
approximately 2-3
weeks.
• C. elegans has a
generation time of
approximately 3
days
Important Phenotypes
 Wildtype (wt)
him-8 =
 unc-76 =
 dpy-13 =
Today:
• Learn how to use the scopes
• Observe males and hermaphrodites