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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

quinlan-roberts
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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. Example: P1 X yellow, round green, wrinkled GGWW ggww F1 All yellow, round Dihybrid cross GgWw

  3. F1 F1 X All yellow, round All yellow, round GgWw GgWw Dihybrid cross con’t: F2

  4. 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

  5. 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

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

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

  8. *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

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

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

  11. Chapter 4: Modification of Mendelian Ratios Allele *Wild-type allele *Mutant allele Conventional symbols for alleles: recessive allele- initial letter of the name of the recessive trait, lowercased and italicized dominant allele- same letter in uppercase Genetic nomenclature is extremely diverse!

  12. Cross between parents with contrasting traits:Red flowersor white flowers Offspring with an intermediate phenotype: pink flowers Incomplete or Partial Dominance

  13. Codominance: Example: MN Blood group- red blood cells contain a transmembrane glycoprotein (glycophorin); two different forms of this protein exist, M and N

  14. Multiple Alleles: Examples: *Table 4.1: over 100 alleles at a given locus in Drosophila *ABO Blood group in humans *Characterized by the presence of glycoprotein antigens on the surface of red blood cells *Distinct from the M and N antigens *Also exhibits codomiance

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