02 - Gregor Mendel Versuche ber Pflanzenhybriden The First...

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MCB140, 25-01-08 1 Gregor Mendel Versuche über Pflanzenhybriden The First Law
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MCB140, 25-01-08 2 The starting material “In all, 34 more or less distinct varieties of Peas were obtained from several seedsmen and subjected to a two year's trial. All the … varieties yielded perfectly constant and similar offspring; at any rate, no essential difference was observed during two trial years. For fertilization 22 of these were selected and cultivated during the whole period of the experiments. They remained constant without any exception.” http://www.mendelweb.org/CollText/homepage.html
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MCB140, 25-01-08 3 “Pure-breeding line” An awkward phrase that is best retired, but never will be. It refers to an organism that exhibits a particular trait (e.g., seed color), and all progeny of that organism (whether it is selfed, or outcrossed to another such organism) also exhibit that trait. Pure-breeding lines are best made by selfing, or brother-sister crosses (like Nefertiti).
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MCB140, 25-01-08 4 “An SCN9A channelopathy causes congenital inability to experience pain” “The index case for the present study was a ten- year-old child, well known to the medical service after regularly performing 'street theatre'. He placed knives through his arms and walked on burning coals, but experienced no pain. He died before being seen on his fourteenth birthday, after jumping off a house roof.” Cox et al. Nature. 2006 444:894-8.
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MCB140, 25-01-08 5 William Ernest Castle – founder of mouse genetics (UCB 1936-1962) 1. Inbreeding as a tool for making genetically uniform strains of mice that are homozygous for every allele in the genome. 2. Brother-sister matings – makes 12.5% of all loci in the genome homozygous (Clarence Little). Why? – homework!! After 40 generations of brother-sister mating, >99.98% of genome is homozygous. By F 60 , mice are considered genetically identical to one another.
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MCB140, 25-01-08 6 Mendel picked the pea as the system. What traits to pick? “Experiments which in previous years were made with ornamental plants have already provided evidence that the hybrids, as a rule, are not exactly intermediate between the parental species . With some of the more striking characters, those, for instance, which relate to the form and size of the leaves, the pubescence of the several parts, etc., the intermediate, indeed, is nearly always to be seen; in other cases, however, one of the two parental characters is so preponderant that it is difficult, or quite impossible, to detect the other in the hybrid.” http://www.mendelweb.org/CollText/homepage.html
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MCB140, 25-01-08 7
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MCB140, 25-01-08 8 The reaffirmation of a known phenomenon Mendel is pointing out the distinction between two “types” of traits. 1.
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This note was uploaded on 08/01/2008 for the course MCB 140 taught by Professor Urnov during the Spring '08 term at University of California, Berkeley.

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02 - Gregor Mendel Versuche ber Pflanzenhybriden The First...

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