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BIOLOGY 205/SECTION 7 DEVELOPMENT- LILJEGREN Lecture 2 MODEL ORGANISMS USED TO STUDY DEVELOPMENT 1. A brief introduction to six model systems widely used in labs today a. Why model organisms? Kit example b. Megabase genome =1,000,000 (million) base pairs; Gigabase = 1 billion! 2. Rules of evidence There are three main types of evidence that are accepted in all of experimental biology when figuring out a gene’s function. It is important to KNOW THEM: Correlative Evidence o You see a gene expressed in a tissue o Weak, but relatively easy Loss of Function Evidence o You knock out the gene, the tissue fails to form. o Better, but a little harder. Gain of Function Evidence o You express a gene in an inappropriate tissue, and transform it. o Best, but hardest of all Or to sum it all up, think of the motto: “Find it, Lose it, Move it” . [but use the formal terms above in an exam situation!!] Oogenesis Behind every successful embryo stands a hard-working mother. 1. While both parents contribute DNA (the developmental blueprint), the mother also contributes two key ingredients to the egg a. a store of supplies providing for embryogenesis b. asymmetric cues to establish embryo's anterior-posterior & dorsal-ventral axes 2. Eggs are assembled in a complex, multi-stage process called OOGENESIS . a. Eggs are very large cells ! They range from 100 μ m (humans) to 1 mm (frogs, fish, fruit flies) to 1-10 cm (birds and reptiles). So even human eggs, although they seem small in comparison are 5x a typical somatic cell (20 μ m) b. Eggs contain large stores of nutrients , called the yolk . Allow at least earliest c. Eggs contain large stores of macromolecules - machinery to synthesize & package DNA & assemble cells. (macromolecules include mitochondria, RNA/DNA polymerases, ribosomes) d. Eggs are enclosed in a coat or shell to: i. ii. regulate sperm entry. 3.
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This note was uploaded on 05/26/2011 for the course BIO 205 taught by Professor Reed during the Spring '11 term at UNC.

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