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Caenorhabditis elegans


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brief about Caenorhabditis elegans

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Caenorhabditis elegans

  1. 1. Kingdom Animalia Phylum Nematoda Class Chromadorea Order Rhabditida Family Rhabditidae Genus Caenorhabditis Species C elegans A tiny nematode; lives in garden soil, feeding on bacteria
  2. 2.  Free-living, transparent nematode, about 1 mm in length, lives in temperate soil environments.  Unsegmented, vermiform, and bilaterally symmetrical.  Has cuticular integument, four main epidermal cords, and a fluid-filled pseudocoelomate cavity  Generally feeds on bacteria.  C. elegans has two sexes: hermaphrodites and males
  3. 3.  Males have a single-lobed gonad, vas deferens, and a tail specialized for mating.  Hermaphrodites have two ovaries, oviducts, spermatheca, and a single uterus.  The hermaphrodite gonad produces first sperm and then oocytes
  4. 4. Hermaphrodites have about 10 eggs inside--the older eggs are laid about as fast as new eggs are made Oocytes pass into the spermatheca and are fertilized. Embryos develop in the uterus, and have a few cleavages before the eggs are laid, so the embryos have a few dozen cells when the embryos are laid. The embryos develop into worms over the next 8-18 hours
  5. 5.  Simple body organization  Easy to grow  Short life cycle: 3 days per generation  Powerful genetics (both self-fertile and cross-fertile)  Transparent body wall  Small size  Invariant  Fully described anatomy and development  Post-genomic tools -- RNAi
  6. 6.  Simplest organisms with a nervous system.  It is an eukaryote, shares cellular and molecular structures and control pathways with higher organisms.  It goes through a complex developmental process, including embryogenesis, morphogenesis, and growth to an adult.  The biological information obtained from C. elegans may be directly applicable to more complex organisms.  About 35% of C. elegans genes have human homologs.
  7. 7.  C. elegans was the first multicellular organism to have its genome completely sequenced  Young, freshly starved larvae best survive freezing in 15% glycerol solution, can also be stored at −80 °C for over ten years  About 35% to 45% of the worms stored in liquid nitrogen survive.
  8. 8.  There are six chromosomes: five pairs of autosomes and the sex chromosome, X  Hermaphrodites have two X chromosomes (XX).  Males have one X chromosome (XO); having only one chromosome instead of a pair is called the hemizygous state.
  9. 9.  It lives a total of about 2 weeks.  The eggs are fertilized within the adult hermaphrodite and laid at about the 40 cell stage  They hatch and it proceeds through 4 larval stages  C. elegans can adopt an alternative life form, called the dauer larval stage in unfavorable conditions.  Dauer larvae are thin and can move but their mouths are plugged and they cannot eat & can remain viable for three months. General form of life cycle of C elegans
  10. 10. LIFE CYCLE OF C elegans Daurer larvae appear to be non-aging: they can roam around for months and then re-enter the L4 stage when they encounter a food source and live about 15 more days
  11. 11.  RNA interference (RNAi) has been extensively used on C. elegans  C. elegans are fed with transgenic bacteria or injected with RNA into the body cavity that express double-stranded RNA that complements the gene of interest, thereby causing RNA silencing.  Live samples of C. elegans used to explore the effects of zero gravity on muscle development and physiology.  The research was primarily about genetic basis of muscle atrophy, which relates to space travel
  12. 12.  Studying meiosis is considerably simplified in the sperm and egg nuclei in the gonads, the difficulties of heterogeneous cellular populations are eliminated because every nucleus at a given position in the gonad therefore is at roughly the same step in meiosis.  It can also be used to study nicotine dependence because it exhibits behavioral responses to nicotine that parallel those of mammals; e.g., acute response, tolerance, withdrawal, and sensitization.