Biology, 6th Edition

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Greg Steinberg AP Biology Chapter 21 The Genetic Basis of Development A. From a Single Cell to a Multicellular Organism a. Embryonic Development involves cell division, cell differentiation, and morphogenesis. i. A single cell goes through multiple steps to become a multicellular organism. ii. Cells also must be differentiated, and be specialized. iii. The cells also must be placed in the right way, this is morphogenesis. iv. All 3 steps work together to make the organism work. v. Morphogenesis in plants and animals is different; in animals, it is necessary to form the three dimensional organism. In plants, morphogenesis occurs throughout the plants life. b. Models help scientists study life i. Amphibians have larger eggs, and biologists are able to study development on them in both macro and micro levels. ii. To understand broad development principles, the organism chosen is known as the model organism. iii. Modern biologists like to use embryos that are easily observed, organisms that have short generation spans and small genomes. Like when Morgan chose fruit flies to work with. iv. Biologists sometimes look at every cell from fertilization and figure out the organisms complete cell lineage. v. There are numerous different organisms biologists like to use depending on what they want to study. B. Differential Gene Expression a. Different Cells Express Different Genes from the same Genome i. All cells have the same genome, that is, the genome of an eye cell would be the same as the genome of a skin cell. But are genes that are not expressed destroyed? ii.
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bio21 - Greg Steinberg AP Biology Chapter 21 The Genetic...

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