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Week 4, Lecture 2, Mendel

Week 4, Lecture 2, Mendel - 1 26-Sep-09 Gardiner 1 Gregor...

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Unformatted text preview: 1 26-Sep-09 Gardiner 1 Gregor Mendel Fig. 12-2, p. 236 B I O L O G Y 0 2 3 26-Sep-09 Gardiner 2 Heredity Historical Perspective • For much of human history people were unaware of how heredity worked • Greek philosophers – male flowers caused female flowers to open – seeds produced by various body parts and transmitted to offspring at time of conception • During 1700’s Anton van Leeuwenhoek saw “animalcules” in sperm of humans and animals • Some scientists speculated they saw little man in each sperm • Pangenesis – males and females formed “pangenes” in every organ • These pangenes then moved through their blood to the genitals and then to children • Concept originated with Greeks and influenced biology up to around 100 years ago • The terms “blood relative”, “full-blooded” and “royal blood” • Francis Galton (Darwin’s cousin) disproved the theory in the 1870’s B I O L O G Y 0 2 3 26-Sep-09 Gardiner 4 Gregor Mendel • Grew up on a farm in what is now Czech Republic (Austria) • 1843 entered monastery • University of Vienna • Became a teacher • Interest in breeding plants at monastery B I O L O G Y 0 2 3 26-Sep-09 Gardiner 5 Why peas ? • Mendel also worked with other species •-Peas worked better •-Peas had 7 traits that gave results Mendel could understand •-Other traits he could not • Rule # 1 of good science – Work with things that work! Mendel’s 7 Pairs of Contrasting Pea Traits As in Fig. 11.4 2 Mendel’s Methods • Emasculation • Cross-pollination • Careful observation of progeny • Statistical interpretation of the results Like Fig. 11.3 • In a typical breeding experiment, Mendel would cross-pollinate ( hybridize ) two contrasting, true-breeding pea varieties. – The true-breeding parents are the P generation and their hybrid offspring are the F 1 generation . • Mendel would then allow the F 1 hybrids to self-pollinate to produce an F 2 generation. • It was mainly Mendel’s quantitative analysis of F 2 plants that revealed the two fundamental principles of heredity: the law of segregation and the law of independent assortment. B I O L O G Y 0 2 3 26-Sep-09 Gardiner 9 Terms • Character – a heritable feature • Trait – a variant of a character • True-breeding – organisms which when they breed produce the same characters • Hybridization – mating or crossing of two varieties • Monohybrid cross...
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Week 4, Lecture 2, Mendel - 1 26-Sep-09 Gardiner 1 Gregor...

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