Biology Chapter 14 - Chapter14 Overview:...

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Chapter 14 Mendel and the Gene Idea Overview: Drawing from the Deck of Genes Every day we observe heritable variations (such as brown, green, or blue eyes)  among individuals in a population. These traits are transmitted from parents to offspring. One possible explanation for heredity is a “blending” hypothesis. o This hypothesis proposes that genetic material contributed by each parent mixes  in a manner analogous to the way blue and yellow paints blend to make green. o With blending inheritance, a freely mating population would eventually give rise to  a uniform population of individuals. o Everyday observations and the results of breeding experiments tell us that  heritable traits do not blend to become uniform. An alternative hypothesis, “particulate” inheritance, proposes that parents pass on  discrete heritable units, genes, that retain their separate identities in offspring. o Genes can be sorted and passed on, generation after generation, in undiluted  form. Modern genetics began in an abbey garden, where a monk named Gregor Mendel  documented a particulate mechanism of inheritance. Concept 14.1 Mendel used the scientific approach to identify two laws of   inheritance. Mendel discovered the basic principles of heredity by breeding garden peas in  carefully planned experiments, carried out several decades before chromosomes  were observed under the microscope. Mendel’s Experimental, Quantitative Approach Mendel grew up on a small farm in what is today the Czech Republic. In 1843, Mendel entered an Augustinian monastery. Mendel studied at the University of Vienna from 1851 to 1853, where he was  influenced by a physicist who encouraged experimentation and the application of  mathematics to science and by a botanist who stimulated Mendel’s interest in the  causes of variation in plants. o These influences came together in Mendel’s experiments. After university, Mendel taught school and lived in the local monastery, where the  monks had a long tradition of interest in the breeding of plants, including peas. Around 1857, Mendel began breeding garden peas to study inheritance. Pea plants have several advantages for genetic study. o Pea plants are available in many varieties that have distinct heritable features, or  characters,  with different variant  traits.
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o Peas have a short generation time; each mating produces many offspring.
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