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Unit 7: Mendelian Genetics Mrs. Howland Biology 10 Rev. Jan 2016
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ESSENTIAL QUESTIONS ~ ??? How is genetic information passed through generations? How do genes affect the characteristics of an organism?
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UNIT OBJECTIVES: Students will be able to… Analyze Mendel’s experiments Make and interpret a Punnett Square Solve genetics problems Make and interpret a pedigree Make and interpret an karyotype Explain the significance of a hetrozygote advantage
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Why do we look the way we do? We look like OURSELVES, but also a LITTLE BIT like our parents! (No, not twins, it’s the same kid!)
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LOOKING BACK: Meiosis Recall that MEIOSIS is the process of cell division that results in 4 genetically unique daughter cells called GAMETES
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LOOKING BACK: Meiosis GAMETES are combined (1 from father, 1 from mother) in fertilization step of sexual reproduction! GAMETES are the daughter cells produced during meiosis SPERM EGG ZYGOTE is the cell that forms as a result of sperm fertilizing an egg. DNA from both parents are combined
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Law of INDEPENDENT ASSORTMENT What accounts for the differences and similarities in humans and other species? During METAPHASE and ANAPHASE of meiosis, there are 2 possible ways that the chromosomes can line up and separate RESULTS in many different possibilities!
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Gregor Mendel The “Father” of genetics LINK: https://www.youtube.com/watch?v=0vAAf4g5iF8https://www.youtube.com/watch?v=0vAAf4g5iF8
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The Work of Gregor Mendel WHY PEAS? Can be crossed (bred) many times within a much shorter timespan than humans or other animals! FOUR (4) different characteristics that are easily observed: Height, pea color, pea shape, flower color
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VOCABULARY! ALLELE: Different forms of a gene, located in same gene locus (location on chromosome) EXAMPLE: A gene can code for PEA COLOR. Two possible alleles for this gene may be GREEN or YELLOW
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VOCABULARY! TRAIT: A specific characteristic EXAMPLE: Pea color, eye color, height CROSS-POLLINATION: Specific, controlled pollination Allowed Mendel to breed plants and control parents to compare inherited traits HYBRIDS: The offspring from crosses between parents that have different traits EXAMPLE: green pea plant (x) yellow pea plant
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Mendel’s F1 Crosses P = the parents (the 2 plants that were crossed F1 = the first generation of offspring
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When F1 plants reproduce by self-pollination F2 = offspring from F1 generation that self-pollinated
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SEGREGATION When gametes are formed, alleles segregate from one another Each gamete carries a single allele for each gene
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Mendel’s Pea Plants Mendel discovered that a hybrid cross resulted in 3 of one trait and 1 of the other in F2 generation (3:1 ratio or 75% and 25%)
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Why did Mendel see these results? LINK: https://www.youtube.com/watch?v=Mehz7tCxjSE https://www.youtube.com/watch?v=Mehz7tCxjSE
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CLASSWORK/HOMEWORK Color plate: Mendel’s Genetics (due at END OF CLASS) PACKET: (11.1) The Work of Gregor Mendel (due NEXT CLASS, P5=Tues 1/26, P1=Wed 1/27)
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Learning the LINGO… Homozygous = Organisms that have TWO (2) of the same alleles for a gene HOMOZYGOUS
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Learning the LINGO… Heterozygous = Organisms that have TWO (2) different alleles for a gene HETEROZYGOUS
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Learning the LINGO… Genotype = Genetic makeup (the set of alleles) Phenotype = Physical traits (determined by alleles)
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Genotype vs. Phenotype
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Learning the LINGO… DOMINANT = Allele that is expressed, even if it is paired with a recessive allele Usually a CAPITAL letter: BB or Bb Recessive = Allele that is only expressed when paired with another recessive allele Usually a lower-case letter: bb
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Dominant vs. Recessive
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Punnett Square, Simple Cross
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Punnett Square (Simple) EXAMPLE KEY: A = a =
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Punnett Square: TRY THIS ONE! Which trait is DOMINANT? How do you know? Which trait is RECESSIVE? How do you know? KEY:
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Looking at: TWO TRAITS DIHYBRID cross ~ a cross between offspring in the F1 generation that have different alleles for TWO traits Recall that LAW of INDEPENDENT ASSORTMENT states that alleles separate independently from one another Allele for 1 trait do not affect alleles for another trait
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Determining Segregated Alleles for crosses with TWO TRAITS Use the FOIL method!! F = FIRST O = OUTSIDE I = INSIDE L = Last
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Crossing TWO TRAITS - Dihybrid Punnett Squares are a lot bigger this time! EXAMPLE: Lab mice, 2 alleles for fur
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Phenotypic Ratios ~ Dihybrid KEY: A = purplea = white B = tallb = short Ratio is 9:3:3:1
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Try it! Complete this cross:
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