150-13MendelianGenetics[1]

150-13MendelianGenetics[1] - Foundations of Biological...

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Foundations of Biological Science I (BioSci 150) C Early ideas about heredity Pangenesis : Aristotle’s informational particles Homunculi : spermists vs ovists, a biological WYSIWYG (‘what you see is what you grow’) Spontaneous generation: a supernatural explanation of life. ..
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Foundations of Biological Science I (BioSci 150) C The problem in explaining heredity: You may look like your parents… or not! The seemingly random inheritance of traits arose because early breeders of animals looked at the ‘whole’ organism; Gregor Mendel chose to follow the inheritance of single, well-defined traits.
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Foundations of Biological Science I (BioSci 150) C Inheritance not only looks like a crapshoot, in many ways it is! But, Mendel, a student of probabilities, knew that truly random events could be predicted! What are the odds of a coin coming up heads? What are the odds of a coin coming up heads twice in a row?
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Foundations of Biological Science I (BioSci 150) C Mendel Realized that inheritance should obey the laws of probability. Rediscovered the particulate nature of the gene by focusing on single traits. This was possible because of true-breeding characters and the advantages of peas. ..
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Foundations of Biological Science I (BioSci 150) C Mendel could make clear observations because the pea plant was a good experimental system. .. Anthers (produce pollen grains, which contain male gametes) Ovules (produce female gametes) stigma
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Foundations of Biological Science I (BioSci 150) C 1. Remove anthers from 1. Remove anthers from flower of one plant. flower of one plant. 2. Collect pollen from the flower of a different plant. 3. Transfer pollen to a stigma of the individual whose anthers have been removed. Crossing pea plants by CROSS-POLLINATION: Crossing pea plants by CROSS-POLLINATION:
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Foundations of Biological Science I (BioSci 150) C A trait is true-breeding if organisms with the trait always produce progeny with the same trait. e.g., Green pea color is true-breeding because breeding plants with green peas always produced new pea plants that produced green peas. Mendel characterized his 7 true breeding traits empirically (by experiment). To understand Mendel’s work we need to understand True Breeding Traits
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Foundations of Biological Science I (BioSci 150) C Mendel studied 7 true- breeding traits with variable phenotypes :
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Foundations of Biological Science I (BioSci 150) C Mendel’s first experiments: Crossing true-breeding plants with opposing traits for the same character. ..
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Foundations of Biological Science I (BioSci 150) C Transfer pollen from round- seeded parent… …to stigma of wrinkled-seeded parent Conclude: Round is dominant over wrinkled, & gender doesn’t matter in pea shape inheritance. One of Mendel’s first crosses… …to stigma of round-seeded parent When the resulting seeds were planted… First half of reciprocal cross Transfer pollen from wrinkled- seeded parent… Second half of reciprocal cross All progeny have round seeds Figure 13.3
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Foundations of Biological Science I (BioSci 150) C
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150-13MendelianGenetics[1] - Foundations of Biological...

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