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Bio_Exam_3_notes_five_star_may_be_better - Bio Exam 3...

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Bio Exam 3 3/11/08 Gregor Mendel – pages 251-255 - BORN 1822 - Monk at the monastery of St. Thomas in Brunn, Czech Republic - Trained in Botany… - 1866 published his work “Experiments with Palnt Hybrids” - 1900 Mendel’s work was redsiscovered by Hugo de Vries in Holland, Carl Correns in Germany and Erich vox Tschermak in Austrua - “particulate” rather than “blending” Mendel worked with edible pea plants - there was John Goss - English 1824 worked with the same plants30 years before Mendel began his work - He observed green and yellow seeds in peas followed time through a number of generations - He observed what Mendel saw Today we speak of Medelian genetic not Gossian - why - Goss didn’t record and count number of seeds Why did Mendel succeed? - he chose the right organism to work with, the edible pea plant o the plant self pollinates, ie self fertilizes o stigma and anthers are completely enclosed by petals until after fertilization o therefore there is no cross contamination Figure 14.2 - he picked the “right” traits to follow - simple single gene inheritance - he followed the crosses for several generations - he was quantitative in his observations (counted and recorded) - he had help from his friends Figure 14.3, table 14.1 Definitions/Terminology - Gene – discrete unit of hereditary information consisting of a specific sequence of DNA. It often codes for a polypeptide chain (a sequence of amino acids) Gene locus
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- a particular position along a specific chromosome where a given gene is located Allele - alternative from of a gene - A,a - B,b - Sometimes superscript or lower case letter (Genetics Problems - on blackboard under assignments - a guide to the kinds of questions you’ll have to answer on the third exam Homozygous - having 2 identical alleles for a trait - AA - Aa - Two superscript big A’s or big B’s - ii Heterozygous - having two different genes (alleles) for a trait - Aa - Superscript AB - S.s. Ai - S.s Bi Figure 14.4 Genotype - refers to the genetic make up of an individual Phenotype - the physical manifestation of a trait o how it appears - determined by the genotype HOW MANY DIFF ALLELES CAN A DIPLOID INDIVIDUAL HAVE AT A SINGLE GENE LOCUS IF THERE ARE 4 ALLELES IN A POPULATION? 2 Dominant Allele - allele that is fully expressed in the phenotype of a heterozygote - only a single copy is required to express the trait - represented by the capital letter (A) Recessive Allele - in a heterozygous individual the allele that is completely masked (not expressed) in the phenotype - rep by lower case letter (a) Why is it not expressed?
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Bio_Exam_3_notes_five_star_may_be_better - Bio Exam 3...

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