Lecture III - Genes-Mutations

Lecture III - Genes-Mutations - Lecture III - Mutation...

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Lecture III - Mutation
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Darwin's Four Basic Postulates Individuals within a population vary in their traits These variations are passed from parent to offspring (hereditable) Some individuals are more successful at surviving and reproducing than others Survival and reproduction are related to the variation in traits among individuals.
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Basis of Variation? Although Darwin's theory was logical, and well supported, it had a number of problems First, the basis of variation Second (the most difficult one), if a new variation appeared, shouldn’t it be diluted in the next generation? Darwin never did solve the second problem satisfactorily
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Gregor Mendel In 1859, an Augustine monk, who taught natural history to high-school students, published a paper that would revolutionize biology Gregor Mendel (1822-1884) wished to study natural history, joining the Augustine order for financial stability Coming from a family of farmers, he had extensive interest in heredity and breeding
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More Mendel Breeding peas in the Monastery garden, he implemented many of the methods that are now considered mandatory for experimentation. These included combinatorics, statistics, large sample sizes, controls, and more These methods were not widespread at the time, and may have contributed to his obscurity So he stayed in his monastery, eventually becoming Abbot, while his work waited 40 years… Illustration of garden peas from the Album Benary seed catalogue, 1876
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Mendel Still So, what did Brother Mendel discover? First and foremost (from an evolutionary point of view) was that the units of inheritance were discrete and were not diluted between generations The laws of Mendelian Genetics: Segregation Independent Assortment
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The Laws of Mendelian Genetics Law of Segregation: Each gene is comprised of two copies of alleles Gametes receive a single allele, so alleles are segregated in the process of gametogenesis Law of Independent Assortment: During the creation of gametes, the way alleles of a gene are divided among the gametes is independent of other genes
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Other Principles of Mendelian Genetics Expression of traits encoded by the genes are determined by dominance patterns among alleles: Complete Dominance: in hybrids, one allele (dominant) is always expressed (the other is recessive) Incomplete Dominance: in hybrids, different levels of mixed phenotype is seen Codominance: in hybrids, both alleles are expressed equally
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Dominance Patterns Complete Dominance http://www.synapses.co.uk/genetics/snap1.gif http://www.gonzaga.org/teachers/dfreedbe/newweb/labGeneticsI_files/image006.jpg Incomplete Dominance
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Mendel is Ignored Mendel’s discoveries, while revolutionary, were largely overlooked for the rest of the 19 th century Mostly because: he published in more obscure journals He lived away from the large universities and intellectual centers His methodology, while advanced for his time, made his
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Lecture III - Genes-Mutations - Lecture III - Mutation...

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