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Unformatted text preview: C. elegans Genetics and Development Genetics can be used as a tool to understand biological problems. Just as biochemistry is used as a tool to understand aspects of cell signaling, for example, genetics can be used as a complementary and equally effective tool to address this problem. What I will discuss in the next few lectures in the use of a model organisms, C. elegans , and how it has been used to study a specific cell signaling pathway. I will digress on occasion from C. elegans , but will always try to return for return to this organism to emphasize essential points. As background for the next few lectures, read from the assigned sections of the book, but I will digress from the book substantially, so the lecture notes will be important. C. elegans Genetics C. elegans is a small free living soil nematode that is easily propagated in the laboratory. It has a short life cycle (3.5 days) and can be maintained on petri plates that have been seeded with E. coli , a C. elegans food source. There are two sexes: self fertilizing hermaphrodites and males. Sex is determined by the X to autosome ratio as in flies. Hermaphrodites have two X chromosomes and a ratio of 1 and males have a single X chromosome (and no Y chromosome) and a ratio of 0.5. A single hermaphrodite makes approximately 1000 oocytes and 300 sperm and produces 300 progeny by self fertilization. Males are produced spontaneously at a frequency of 1/2000 progeny by nondisjunction. A hermaphrodite that has been mated to a male will produce two types of progeny: progeny from self fertilization and progeny from cross fertilization. The self progeny will be all hermaphrodites and half of the cross progeny will be male. To distinguish between self and cross progeny hermaphrodites, the hermaphrodites can be marked. For example, crossing a wild-type male with a Dumpy (Dpy) hermaphrodite (homozygous for a recessive mutation that causes the worms to be short and fat) results in two types of hermaphrodites: self progeny that are Dpy and cross progeny that are not Dpy....
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- Spring '09
- Cell Signaling