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BISC 219/2009: Mod 1 C. elegans General Information: Difference between revisions
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BISC 219/2009: Mod 1 C. elegans General Information (view source)
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== Nematode Lifecycle == | == Nematode Lifecycle == | ||
The development of ''C. elegans'' is known in great detail because this tiny organism (1 mm in length) is transparent and the developmental pattern of all 959 of its somatic cells has been traced. ''C. elegans'' generally reproduces as a self-fertilizing hermaphrodite, with each animal producing BOTH sperm and eggs. Two reflexed gonadal arms (each of which contains an ovary, oviduct, spermatheca, and uterus) terminate at the vulva, located midway along the ventral side. The mature hermaphrodite is effectively a female because the gonad has earlier made and stored sperm before turning to the production of oocytes. Eggs (developing embryos) are fertilized by endogenous sperm and then undergo some development inside the parental hermaphrodite. Embryos are arranged along the uterus with the most developed ones found nearest the vulva. Fertilized eggs are covered with a chitinous shell and, when mature enough, are deposited on the agar surface. Embryogenesis occurs in about 12 hours, development to the adult stage occurs in 2.5 days, and the worm's life span is 2-3 weeks. The entire life cycle takes about 3 1/2 days at 20°C with each adult hermaphrodite producing 250-350 progeny.<br> | '''Embryonic Development''' | ||
The development of ''C. elegans'' is known in great detail because this tiny organism (1 mm in length) is transparent and the developmental pattern of all 959 of its somatic cells has been traced. ''C. elegans'' generally reproduces as a self-fertilizing hermaphrodite, with each animal producing BOTH sperm and eggs. Two reflexed gonadal arms (each of which contains an ovary, oviduct, spermatheca, and uterus) terminate at the vulva, located midway along the ventral side. The mature hermaphrodite is effectively a female because the gonad has earlier made and stored sperm before turning to the production of oocytes. Eggs (developing embryos) are fertilized by endogenous sperm and then undergo some development inside the parental hermaphrodite. Embryos are arranged along the uterus with the most developed ones found nearest the vulva. Fertilized eggs are covered with a chitinous shell and, when mature enough, are deposited on the agar surface. Embryogenesis occurs in about 12 hours. <br> | |||
'''Post-Embryonic Development''' | |||
A newly hatched animal resembles an adult in general proportions and body movement, but is only about one-sixth the length of an adult. During growth, developing larvae undergo four molts in which the old cuticle is shed and replaced by a new underlying cuticle. The inter-molt stages are designated L1 through L4, followed by adulthood. L3 and L4 hermaphrodites can be distinguished from adults via the presence of half-moon shaped structure at the location of the vulva. Worms stop pharyngeal pumping and become lethargic while molting. During growth at 20°C, molting occurs at approximately 14, 22, 30, and 40 hours after hatching, with egg laying commencing at about 50 hours. During larval development, the number of non-gonadal cells increases from about 550 in the newly hatched L1 to about 810 in the mature hermaphrodite and to about 970 in the mature male. At hatching the L1 has only 4 gonadal cells. These cells proliferate to form the adult reproductive system of approximately 2500 nuclei. It is important that you develop some ability to stage animals (that is; recognize the various developmental stages). This is most easily accomplished by simply viewing a mixed population such that you can directly compare the sizes of the various stages. | |||
In summary, development from external egg deposit to the adult stage occurs in 2.5 days, and the worm's life span is 2-3 weeks. The entire life cycle takes about 3 1/2 days at 20°C with each adult hermaphrodite producing 250-350 progeny. | |||
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[[Image:AnatomyLarge.gif]] | [[Image:AnatomyLarge.gif]] | ||
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The molecular genetics of ''C. elegans'' is also very well developed. This nematode holds the distinction of being the first metazoan to have its genome sequenced. In addition, most tricks of the molecular geneticist have been employed in ''C. elegans''. These include making transgenics (including knockouts) and the technique of RNA interference: RNAi. Consult [http://elegans.swmed.edu/ Leon Avery's ''C. elegans'' server] and [http://www.wormbase.org/ Wormbase] for more information about the molecular genetics of the worm. | The molecular genetics of ''C. elegans'' is also very well developed. This nematode holds the distinction of being the first metazoan to have its genome sequenced. In addition, most tricks of the molecular geneticist have been employed in ''C. elegans''. These include making transgenics (including knockouts) and the technique of RNA interference: RNAi. Consult [http://elegans.swmed.edu/ Leon Avery's ''C. elegans'' server] and [http://www.wormbase.org/ Wormbase] for more information about the molecular genetics of the worm. | ||
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[[BISC 219/2009: Mod 1 Media and Tools | Tools and Techniques]]<br> | [[BISC 219/2009: Mod 1 Media and Tools | Tools and Techniques]]<br> | ||
