Chapter 3-2&3

Chapter 3-2&3 - Chapter 3, Part II (of II) Chapter...

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Unformatted text preview: Chapter 3, Part II (of II) Chapter Extensions to Mendel; Multifactorial = Arising from : 1)Interaction of 2 or more genes 2)Interactions between a gene Interactions and other “factors” and Two genes can interact to Two determine one trait one Combined action of 2 genes Two pure-breeding white sweet pea lines Tan and gray lentils What could be a molecular explanation? Two genes can interact to Two determine one trait one Combined action of 2 genes Two pure-breeding white sweet pea lines Tan and gray lentils One gene masks another = _______ Bombay phenotype Coat color Epistasis example: Bombay phenotype Epistasis Epistasis example: coat color B allele is dominant and determines black; b allele is recessive and determines brown. If one gene, BB and Bb = black; bb = brown So where does the yellow come from? BB or Bb (B-) black EE or Ee (E-) brown yellow yellow Default “color” (is essentially colorless) EE or Ee (E-) black brown yellow yellow Default “color” (is essentially colorless) B- E= Black Labrador bb black EE or Ee (E-) brown yellow yellow Default “color” (is essentially colorless) bb E= Brown (“Chocolate”) Labrador BB or Bb (B-) ee black brown -- ee yellow yellow Default “color” (is essentially colorless) = Yellow (Golden) Labrador Two genes can interact to Two determine one trait one Combined action of 2 genes Two pure-breeding white sweet pea lines Tan and gray lentils One gene masks another = ________ Bombay phenotype Coat color Mutation at 1 of 2 or more genes can produce same phenotype A mutant allele at 1 of 2 or more genes mutant yields the same phenotype yields = ______________trait ______________trait Deafness in humans may be caused by a mutant Deafness allele at one of more than 50 different genes allele Albinism _________________test Genetic tool to determine whether a phenotype arises Genetic from mutations in the same or separate genes from Albinism Albinism Complementation Test Complementation The same genotype does not always produce the same phenotype produce Phenotype often depends on _________ Phenotype and____________ and____________ ___________– percentage of a population with a ___________– particular genotype that show the expected phenotype phenotype can be complete (100%) or incomplete (e.g., retinoblastoma can penetrance is 75%) penetrance ___________– degree or intensity with which a ___________– particular genotype is expressed in a phenotype particular can be variable or unvarying affected by: affected 1) Chance 2) Modifier genes (which have subtle, secondary 2) effects on a phenotype) effects 3) Environment Temperature is a common element of the environment that Temperature affects phenotype affects Temperature affects Expressivity in Siamese cats Siamese Coat color in Siamese cats is darker in its extremities (legs, tails, ears, etc.) because of a mutation that renders an enzyme involved in melanin synthesis temperature sensitive Continuous variation can be explained by Mendelian analysis explained Previous examples of Mendelian inherited traits were Previous discontinuous, clear cut phenotypes discontinuous, Continuous traits such as height in humans are Continuous determined by segregating alleles of many genes interacting with one another and the environment interacting Continuous traits are called quantitative traits by Continuous geneticists and are usually polygenic geneticists The more genes that contribute to a trait, the greater the The number of possible phenotypic classes and the greater the similarity to continuous variation the Height and skin color are continuous traits continuous Two genes can interact to Two determine one trait one Combined action of 2 genes Two pure-breeding white sweet pea lines Tan and gray lentils One gene masks another = ________ Bombay phenotype Coat color Mutation at 1 of 2 or more genes can produce same phenotype One gene can interact with other factors to One determine one trait one Penetrance and expressivity Modifier genes Environment Chance ...
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This note was uploaded on 03/28/2010 for the course BIOL 2153 taught by Professor Larkin during the Spring '03 term at LSU.

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