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Mendelian Genetics
 

Mendelian Genetics

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    Mendelian Genetics Mendelian Genetics Presentation Transcript

    • 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
    • A. Before Mendel The blending theory (paradigm) Inheritance of acquired characteristics
      • statistics
      • amateur
      • inductive leap
      Darwin and Mendel
    • B. Mendel’s experimental approach Hermaphrodite Perfect flowers pollen egg Genetic barriers
    • Pea plant traits
    • Pure breeding lines Breed true
      • 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
    • 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
    • Human traits Hand folding
    • III. Genetic crosses Punnett Square
    • III. Genetic crosses
    • 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%
      • Monohybrid cross: genetic disorders and lethal genes
    •  
      • 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
    • Sickle cell trait: recessive disorder
    • Sickle cell trait: recessive disorder Homozygous dominant = normal, not malaria resistant Heterozygous = malaria resistant Homozygous recessive = sickle cell anemia
    • 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?
    • Dwarfism : dominant trait Homozygous dominant = lethal Heterozygous = dwarf Homozygous recessive = normal height Hardy-Weinburg rule
    • 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
    • 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
    • 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
    • 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.
    • B. Principle of independent assortment Different genes on different chromosomes segregate into gametes independently of each other.
    • C. Genes are particles
    • V. Eugenics Francis Galton Social Darwinism Positive Eugenics
    • Eugenics
    • Eugenics
    • Eugenics today? IVF/ PGD Gene “therapy”
    • The end