Biol168_10F_Lecture 9_13Oct2010

Biol168_10F_Lecture 9_13Oct2010 - Dr Morris Maduro UC...

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Dr. Morris Maduro, UC Riverside Biology 168 – 10F – Lecture 9, page 1 Lecture #9: Early C. elegans Development Textbook: 2nd edition: p. 52-54; pp. 191-201; 3rd edition: 185-195. Caenorhabditis elegans as a Model Organism C. elegans got its start about 40 years ago when Sydney Brenner decided that, after having solved the problems of gene expression (the genetic code and messenger RNA), that it was time to look to a model animal to solve more complicated problems, in particular the nervous system . Work in C. elegans has been recognized internationally in the past several years. Two separate Nobel Prizes in Physiology or Medicine have been awarded: First in 2002, to John Sulston, Robert Horvitz and Sydney Brenner (for studying the cell lineage and cell death); in 2006, to Craig Mello and Andrew Fire (for the discovery of RNA interference, or RNAi); and in 2008 to Martin Chalfie (for using GFP as a reporter). C. elegans exists in two sexes, males and hermaphrodites (females that make sperm for a short time, then switch to making oocytes). Their complete life cycle takes about three days. They are optically transparent at all life stages, facilitating light microscopy, in particular the use of Nomarski or Differential Interference Contrast (DIC) microscopy. The fertilized egg takes 12 hours to complete development: The first half consists mostly of cell divisions, and the latter half, of morphogenesis. The worm hatches as a juvenile about 150 μ m long, and it will undergo four molts to become an adult. The hermaphrodite has 959 somatic cells. The pattern of cell divisions is the same from animal to animal, and development is mosaic . C. elegans is considered a triploblastic (three germ layers) organism as it contains tissues consistent with three germ layers . The complete lineage , or pattern of cell divisions (the first few of which are shown below) was deduced by John Sulston and colleagues. The zygote (P 0 ) undergoes asymmetric cell divisions to generate six founder cells , each of which will undergo a stereotyped pattern of cleavages with characteristic periodicity. The lineage gives the impression that the
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This note was uploaded on 10/28/2010 for the course BIOL 168 taught by Professor Maduro during the Spring '10 term at UC Riverside.

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Biol168_10F_Lecture 9_13Oct2010 - Dr Morris Maduro UC...

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