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Mendelian Genetics


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  • 1. Inheritance: Mendelian Genetics I. Gregor Mendel (1865) A. Before Mendel B. Mendel’s experimental approach II. Genetic terms 1. genes 2. gene pair 3. alleles 4. homozygous/heterozygous 5. dominant/recessive 6. homozygous dominant and recessive/heterozygous 7. genotype/phenotype III. Genetic crosses A. Monohybrid crosses B. Dihybrid crosses IV. Mendel's discoveries A. Principle of segregation B. Principle of independent assortment C. Genes are particles
  • 2. A. Before Mendel The blending theory (paradigm) Inheritance of acquired characteristics
    • statistics
    • amateur
    • inductive leap
    Darwin and Mendel
  • 3. B. Mendel’s experimental approach Hermaphrodite Perfect flowers pollen egg Genetic barriers
  • 4. Pea plant traits
  • 5. Pure breeding lines Breed true
  • 6.
    • Why was Mendel’s experimental findings ignored during
    • his lifetime?
    • He was an amateur
    • There was a problem with inductive leaps
    • The dominant paradigm was opposed to his findings
    • He used statistics
    • All of the above
  • 7. II. Genetic terms 1. genes/ loci 2. gene pair = homologues 3. alleles 4. homozygous/heterozygous 5. dominant/recessive 6. homozygous dominant and recessive/heterozygous 7. genotype/phenotype
  • 8. Human traits Hand folding
  • 9. III. Genetic crosses Punnett Square
  • 10. III. Genetic crosses
  • 11. Red coat in foxes is a dominant trait; white is the recessive trait. If a red fox whose mother had a white coat is bred to a white fox, what will be the probable percentage of red kits (baby foxes)? a. 25% b. 50% c. 75% d. 100%
  • 12.
    • Monohybrid cross: genetic disorders and lethal genes
  • 13.  
  • 14.
    • Tay-Sachs is a lethal disorder resulting in death by the
    • age of 4. A couple who are normal have a child with Tay-
    • Sachs. Which of the following is true of the parents?
    • One parent is homozygous dominant and the other is
    • homozygous recessive
    • b. both parents are heterozygous
    • c. both parents are homozygous dominant
    • d. both parents are homozygous recessive
  • 15. Sickle cell trait: recessive disorder
  • 16. Sickle cell trait: recessive disorder Homozygous dominant = normal, not malaria resistant Heterozygous = malaria resistant Homozygous recessive = sickle cell anemia
  • 17. Huntington’s disease: dominant disorder CAGCAGCAG Normal, 26 times HD, 40 to >100 times Manifests after age 40 Why is dominant lethality less common than recessive?
  • 18. Dwarfism : dominant trait Homozygous dominant = lethal Heterozygous = dwarf Homozygous recessive = normal height Hardy-Weinburg rule
  • 19. If two achondroplasic dwarfs have children, what fraction of the children would be expected to be dwarfs like their parents? a. 1/4 b. 1/2 c. 2/3 d. 3/4
    • What determines how common a trait is in a population?
    • it’s frequency
    • Dominance
    • Selection
    • Chance
  • 20. B. Dihybrid crosses: Human traits Dimples dominant to no dimples Brown eyes dominant to blue Dark hair dominant to light hair Curly hair incompletely dominant to straight hair
  • 21. In humans, a widow's peak is dominant and a straight hairline is recessive. Dimples are dominant and no dimples are recessive. A male who is heterozygous for both widow's peak and dimples has a child with a woman who has a straight hairline and no dimples. What is the phenotype ratio of children can they produce? a. 3: 1 b. 2:2 c. 1:1:1:1 d. 4:0
  • 22. IV. Mendel’s discoveries A. Principle of segregation Sexually reproducing diploid organisms have 2 alleles of each gene. These 2 alleles segregate from each other to form gametes that contain only 1 allele of each gene.
  • 23. B. Principle of independent assortment Different genes on different chromosomes segregate into gametes independently of each other.
  • 24. C. Genes are particles
  • 25. V. Eugenics Francis Galton Social Darwinism Positive Eugenics
  • 26. Eugenics
  • 27. Eugenics
  • 28. Eugenics today? IVF/ PGD Gene “therapy”
  • 29. The end