chap14 - Genes, Development, and Evolution Chapter 14...

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Unformatted text preview: Genes, Development, and Evolution Chapter 14 EVOLUTION IS THE GENETIC CHANGE OCCURRING IN A POPULATION OF ORGANISMS OVER TIME Changes in the gene pool (allele frequency) of a species from one generation to the next as a consequence of such processes as natural selection, genetic drift, and mutation. Development Involves Distinct but Overlapping Processes Development the process by which a multicellular organism undergoes a series of changes, taking on forms that characterize its life cycle. After the egg is fertilized, it is called a zygote . In its earliest stages, a plant or animal is called an embryo . The embryo can be protected in a seed, an egg shell, or a uterus. Development (Part 1) Development (Part 2) Development Involves Distinct but Overlapping Processes Four processes of development: Determination sets the fate of the cell Differentiation is the process by which different types of cells arise Morphogenesis is the organization and spatial distribution of differentiated cells Growth is an increase in body size by cell division and cell expansion As zygote develops, the cell fate of each undifferentiated cell drives it to become part of a particular type of tissue. Experiments in which specific cells of an early embryo are grafted to new positions on another embryo show that cell fate is determined during development. A Cells Fate Is Determined in the Embryo Determination is influenced by changes in gene expression as well as the external environment. Determination is a commitment; the final realization of that commitment is differentiation . Differentiation is the actual changes in biochemistry, structure, and function that result in cells of different types. Determination is followed by differentiation under certain conditions a cell can become undetermined again. It may become totipotent able to become any type of cell. Plant cells are usually totipotent but can be induced to dedifferentiate into masses of calli , which can be cultured into clones . Genomic equivalence all cells in a plant have the complete genome for that plant. In animals, nuclear transfer experiments have shown that genetic material from a cell can be used to create cloned animals. The nucleus is removed from an unfertilized egg, forming an enucleated egg. A donor nucleus from a differentiated cell is then injected into the enucleated egg. The egg divides and develops into a clone of the nuclear donor. As in plants, no genetic information is lost as the cell passes through developmental stagesgenomic equivalence. Practical applications for cloning: Expansion of numbers of valuable animals Preservation of endangered species Preservation of pets In plants, growing regions contain meristems clusters of undifferentiated, rapidly dividing stem cells....
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chap14 - Genes, Development, and Evolution Chapter 14...

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