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11 – Introduction to Genetics. The Work of Gregor Mendel. Inheritance other than $$$$ How did things get passed on? Genetics – the scientific study of heredity Mendel, peas and his work Long overlooked. The Role of Fertilization. Male and Female Parts

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the work of gregor mendel
The Work of Gregor Mendel
  • Inheritance other than $$$$
  • How did things get passed on?
    • Genetics – the scientific study of heredity
  • Mendel, peas and his work
    • Long overlooked
the role of fertilization
The Role of Fertilization
  • Male and Female Parts
    • Fertilization – joining of reproductive cells
    • Self-pollination
      • True breeding
    • Trait
      • Cross Breeding
        • Male parts gone
    • Hybrids
genes and alleles
Genes and Alleles
  • P1 and F1 generations
  • Disappearance of traits
  • Parent to offspring by genes.
    • Mendel called them factors
  • Single gene trait (ex. Tall vs. Short)
  • Alleles – forms of a gene
dominant and recessive alleles
Dominant and Recessive Alleles
  • Principle of Dominance
    • Mendel’s second conclusion
  • One dominant allele
    • Organism shows that trait
  • Recessive Alleles
    • Only show when dominant is not present
segregation
SEGREGATION
  • What happened to the other trait?
    • Was it still in the F1?
  • Did an F2 cross
    • Trait reappeared
  • Mendel assumed Dominance masks
f1 cross and gametes
F1 Cross and Gametes
  • One trait separated from the other
    • Segregation
    • During gamete formation
      • Follow this chart
11 2 applying mendel s principles probability and punnett squares
11.2 Applying Mendel’s Principles – Probability and Punnett Squares
  • Probability – likelihood that an event would occur.
    • Mendel analyzed his data
    • Found probability
  • Segregation and Outcomes –
    • Alleles segregate during gamete formation (haploid)
    • Homozygous vs. Heterozygous
probabilities averages genotype and phenotype
Probabilities, Averages, Genotype and Phenotype
  • Probabilities predict the average outcome
  • Genetic makeup vs. observable characteristics
    • Genotype vs. Phenotype
  • Punnett Squares
    • Uses math to predict
independent assortment
Independent Assortment
  • Does segregation of one pair affect other pairs?
    • Two factor (dihybrid) cross
    • Followed two traits
      • F1
      • F2
      • Independent Assortment
        • Some genes separate independent of each other
summary of mendel
Summary of Mendel
  • Characteristics are determined by genes and passed from parents
  • If there are two or more forms of alleles some may be dominant or recessive
  • Most adults have two copies of each gene (one from mom and one from dad) and the segregate during gamete formation
  • Alleles usually segregate independent of each other
summary
Summary
  • Thomas Hunt Morgan
    • Showed that the same principles apply to animals
    • Fruit Fly (Drosophila melanogaster)
beyond dominant and recessive
Beyond Dominant and Recessive
  • Incomplete Dominance
    • Traits blend
  • Codominance
    • Both traits show
  • Multiple Allele
    • More than two alleles
  • Polygenic
    • Several Genes involved
genes and environment
Genes and Environment
  • Environment can affect gene expression
    • Phenotype is determined by genotype and environment
    • Western White Butterfly
      • Pigment changes
      • Why?
chromosome number
Chromosome Number
  • Diploid Cells
    • Homologous pairs
      • Diploid (2N)
    • Inherited from each parent
    • Segregate during gamete formation
  • Haploid Cells
    • Single set of chromosomes
phases of meiosis
Phases of Meiosis
  • Meiosis
    • Chromosome # cut by half
  • Prophase I
    • Tetrad
    • Crossing over
  • Metaphase I and Anaphase I
    • Paired homologous chromosomes line up
phases of meiosis1
Phases of Meiosis
  • Telophase I and Cytokinesis
    • Results in 2 daughter cells
    • Haploid in number
  • Prophase II
    • No tetrads
  • Metaphase II, Anaphase II, Telophase II and Cytokinesis
    • Similar to Meiosis I but four daughter cells result (gametes) (zygote)
comparing meiosis and mitosis
Comparing Meiosis and Mitosis
  • Replication and Separation of Genetic Material
    • Mitosis
      • Replicate once, divide once (single chromosomes lined up, full set of chromosomes at end
    • Meiosis
      • Replicate once, divide twice (pairs lined up), half the number of chromosomes at end.
gene linkage and gene maps
Gene Linkage and Gene Maps
  • Gene Linkage (Thomas Hunt Morgan)
    • Traits assort independently IF
      • they are on different chromosomes or
      • Very far apart on same chromosome
    • If they are fairly close on the same chromosome, they are LINKED
  • Distance apart on the chromosome is key
    • The closer the genes are, the more linked they are
  • Maps are made based on how often crossing over is observed
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