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Review:

Review:. *Unit factors in pairs- genetic characteristics are controlled by unit factors that exist in pairs in individual organisms *Principle of Dominance and Recessiveness- one factor is dominant over the recessive one

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Review:

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  1. Review: *Unit factors in pairs- genetic characteristics are controlled by unit factors that exist in pairs in individual organisms *Principle of Dominance and Recessiveness- one factor is dominant over the recessive one *Law of Segregation- During gamete formation the paired unit factors segregate randomlyso that each gamete receives one or the other *Law of Independent Assortment – During gamete formation, segregating pairs of unit factors assort independently of each other

  2. Independent Assortment

  3. Example: P1 X gw yellow, round green, wrinkled gw GGWW ggww gw F1 gw All yellow, round Dihybrid cross Punnett square and the law of independent assortment: GW GW GW GW GgWw

  4. F1 F1 X GW All yellow, round All yellow, round Gw GgWw GgWw gW gw 9:3:3:1 Phenotypic ratio; Genotypic ratio as follows: 1/16 GGWW, 2/16 GGWw, 2/16 GgWW, 4/16 GgWw 9/16 yellow, round 1/16 GGww, 2/16 Ggww 3/16 yellow, wrinkled 1/16 ggWw, 2/16 ggWw 3/16 green, round 1/16 ggww 1/16 green, wrinkled Punnett square and the law of independent assortment: Dihybrid cross con’t: GW Gw gW gw F2

  5. Example: Theoretical gene pairs represented by the symbols A, B, and C P1 AABBCC aabbcc X ABC abc Gametes: F1 AaBbCc Gametes: ABC ABc AbC Abc aBC aBc abC abc The Trihybrid Cross: Trihybrid cross

  6. The Forked-Line Method (branch diagram): Recall: *The F1 that result from a monohybrid cross (AA x aa) all have the genotype Aa and the phenotype represented by A *The F2 that result from a cross between 2 individuals from the F1, have a phenotypic ratio of 3:1

  7. The Forked-Line Method (branch diagram):

  8. The Forked-Line Method (branch diagram): *NOTE: We are assuming that independent assortment of these 3 gene pairs is a random process!

  9. *Hugo de Vries *Karl Correns *Erich Tcshermak Mendel Rediscovered: Why did Mendel’s work go unnoticed for so long? Charles Darwin and Alfred Russel Wallace: continuous variation – offspring were a blend of parents’ phenotypes *1879 Walter Flemming *early 20th century *1902 Walter Sutton and Theodor Boveri Chromosomal Theory of Inheritance

  10. How do we account for genetic variation? Cross over: *Independent assortment *Crossing over *Random fertilization Independent Assortment:

  11. = Female = Male =Unknown Human Pedigrees Pedigree *Proband (p)

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