Biological Evolution

Biological Evolution - Evolution and Genetics Darwin...

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Evolution and Genetics Evolution and Genetics Darwin Double-Helix of DNA
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Genetics and Mendel The science of genetics explains the origin of the variety upon which natural selection operates. The study of hereditary traits was begun in 1856 by Gregor Mendel, an Austrian monk. By experimenting with successive generations of pea plants, Mendel came to the conclusion that heredity is determined by discrete particles, the effects of which may disappear in one generation, and reappear in the next.
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Genetics and Mendel Mendel’s second set of experiments with pea plants. Dominant colors are shown unless otherwise indicated.
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Genetics and Mendel Mendel determined that the traits he observed occurred in two basic forms: dominant and recessive. Dominant forms manifest themselves in each generation. Recessive forms are masked whenever they are paired with a dominant form of the same trait in a hybrid individual. It has since been demonstrated that some traits have more than these two forms—human blood type, for example, has several forms, some of which are codominant .
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Genetics and Mendel Punnett square of a homozygous cross and a heterozygous cross. These squares show how phenotypic ratios of the F1 and F2 generations are generated. Colors show genotypes.
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Genetics and Mendel The traits Mendel identified occur on chromosomes . Humans have twenty three matched pairs of chromosomes, with each parent contributing one chromosome to each pair. Chromosomes contain several genes , or genetic loci, which determine the nature of a particular trait. A trait may be determined by more than one gene. Alleles are the biochemically different forms which may occur at any given genetic locus. Chromosome pairs’ loci may be homozygous (identical alleles) or heterozygous (mixed).
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Genetics and Mendel Mendel also determined that traits are inherited independently of one another. The fact that traits are transmitted independently of
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This note was uploaded on 02/21/2012 for the course ANTH 101 taught by Professor Simmons during the Spring '06 term at South Carolina.

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Biological Evolution - Evolution and Genetics Darwin...

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