Chapter 14 - Chapter 14 Mendel and the Gene Idea Chapter 14...

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Chapter 14 - Mendel and the Gene Idea Chapter 14 Mendel and the Gene Idea Lecture Outline 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 will 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 model, “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. Mendel grew up on a small farm in what is today the Czech Republic. In 1843, Mendel entered an Augustinian monastery. He 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. These influences came together in Mendel’s experiments. After university, Mendel taught at the Brunn Modern School and lived in the local monastery. The monks at this monastery 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 with distinct heritable features, or characters, with different variant traits. o Mendel could strictly control which plants mated with which.
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o Each pea plant has male (stamens) and female (carpal) sexual organs. o In nature, pea plants typically self-fertilize, fertilizing ova with the sperm nuclei from their own pollen. o However, Mendel could also use pollen from another plant for cross-pollination. Mendel tracked only those characters that varied in an “either-or” manner, rather than a “more-or-less” manner. o
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Chapter 14 - Chapter 14 Mendel and the Gene Idea Chapter 14...

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