Lecture_17_DulaiS09_GeneticsII

Lecture_17_DulaiS09_ - Genetics Principles of inheritance Mendelian Genetics(2 Lecture 17 Chapters 11.4-11.7 1 Gene Dominance Relations Complete

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1 Genetics: Principles of inheritance Mendelian Genetics (2) Lecture 17 – Chapters 11.4-11.7
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2 Gene Dominance Relations Gene Dominance Relations Complete dominance – Heterozygote (Aa) phenotype is identical to the phenotype of the homozygous dominant (AA) individual Incomplete dominance – Heterozygote phenotype is somewhere between that of two homozygotes Codominance – Non-identical alleles specify two phenotypes that are both expressed in heterozygotes
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3 Example of Incomplete Dominance: Flower Color in Snapdragons • Snapdragons have a red pigment gene that has two alleles: R R (codes for production of red pigment) (codes for production of red pigment) r r (red pigment not produced) (red pigment not produced) • For this character, both genes (on each of the two homologous chromosomes) are functional in a cell. How would these phenotypes be different if R was completely dominant over r ? RR Rr rr
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4 Complete dominance: RR Rr rr Incomplete dominance: RR Rr rr
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5 Incomplete dominance: F 1 generation for true-breeding snapdragons (homozygote RR) (homozygote rr) Plants with red-flowers Plants with white-flowers (heterozygotes Rr) F 1 generation: plants with pink flowers
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6 Incomplete dominance: F 2 generation for true-breeding snapdragons (heterozygote Rr) (heterozygote Rr) F 1 generation: plants with pink flowers (rr) (Rr) (Rr) (RR) Plants with white-, pink-, and red- flowers in a 1:2:1 ratio
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7 Codominance: Blood types are a medically essential example of genetic co-dominance Blood transfusions are an essential part of modern medicine, providing a short-term replacement for any blood loss that a patient cannot replace (e.g. after an accident or during surgery). Over 14 million blood transfusions per year—1 in 10 hospital patients needs blood. Blood transfusions documented since the 1660’s but safe transfusion became possible only with antiseptic practices and blood typing in the early 1900’s
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8 ABO Blood Type: Determined by Glycolipids on Red Blood Cell surfaces •Type A - Glycolipid A on cell surface •Type B - Glycolipid B on cell surface •Type AB - Both glyocolipids A & B •Type O - Neither glyocolipid A nor B A A A A A B B B B B B A B A AB O
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9 The immune system reacts ( transfusion reaction ) to unfamiliar glycolipids (either A or B) on RBC surface A A A A A B B B B B B A B A AB O Patient A A A A A B A B A AB
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This note was uploaded on 11/18/2010 for the course SS 101 taught by Professor Denver during the Spring '10 term at Alabama.

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Lecture_17_DulaiS09_ - Genetics Principles of inheritance Mendelian Genetics(2 Lecture 17 Chapters 11.4-11.7 1 Gene Dominance Relations Complete

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