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Monday, 1/25/10 (Genetics) Check Grades Genetics Lesson Bring Large Milk Cartons (Extra Credit!!) Homework, Due Thursday / Friday Read pgs 165-169 Answer #'s 1-5 pg 169 Tuesday / Wednesday, 1/26-27 More About Genetics Punnett Squares Packet -Single Factor Crosses Thursday / Friday, 1/28-29 Discuss and Collect Homework Correct Punnett Squares Packet #'s 1-10 Plant Corn for Genetics Lab Start Genetics Problems 1
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Genetics
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Gregor Mendel This is Gregor Mendel He loved math He loved peas So he worked at a monastery to find out how certain traits were passed from parents to offspring He studied traits and inheritance
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Peas – The Lucky Plant Most famous for his work with peas Peas come in many varieties Control pollination Peas have distinctive characteristics
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Pea plants have seven observable characteristics. Each characteristic has two possible traits. CharacteristicPossible Trait Plant HeightLong or Short Stems Flower Position on StemAxial or Terminal Pod ColorGreen or Yellow Pod AppearanceInflated or constricted Seed TextureSmooth or Wrinkled Seed ColorYellow or Green Flower ColorPurple or White
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Mendel’s Work On Pea Plants By controlling plant pollination (fertilization), Mendel was able to create pea plants that were true-breeding or “pure” for each trait. True breeding parent plants always produce offspring with the same trait.
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Flower Color Example A plant true-breeding for purple flowers will always produce offspring with purple flowers. True breeding plants are called the P 1 generation.
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Flower Color Example He then crossed a true breeding purple plants with a true breeding white plants This is the P 1 generation
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P 1 Generation = true breeding parent
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Flower Color Example The offspring of the P 1 generation is the F 1 generation 1 st Filial (son/daughter) The offspring were hybrids because the parents had different traits Purple x White All offspring were Purple!
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F 1 = 1 st Offspring Generation
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Dominant and Recessive Purple “beat” White in the F 1 generation Mendel called the trait that appeared in the F1 generation the dominant trait. The trait that did not appear in the F1 generation is the recessive trait.
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Law of Segregation States that for each trait there are 2 controlling factors During gamete formation (meiosis) these 2 factors separate Each gamete gets 1 and only 1 factor When egg is fertilized, the egg now has 2 factors per trait
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Crossing F1 Generation Mendel let the plants from the F1 generation self pollinate. Did this make true breeding plants? No! About ¼ of the plants showed the recessive trait. White
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F 2 Generation
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The White trait was hidden in the DNA
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Law of independent assortment This law states that factors (allele pairs) for different characteristics (gene) separate independently during the formation of gametes. Therefore, traits are transmitted to offspring independently of one another. Example: White flowering plant (recessive) with green pod (dominant)
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Terms Homozygous = Both alleles are the same PP or pp Heterozygous = alleles are different 1 dominant gene, 1 recessive Pp Genotype = Which genes are present PP = purple Pp = purple pp = white Phenotype = Physical appearance, What we see! Punnett Squares
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