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Introduction to Genetics: Mendel's Pea Experiment

Learn about Gregor Mendel, his groundbreaking pea plant experiments, traits, genes vs. alleles, dominance, genotypes, and phenotypes in genetics.

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Introduction to Genetics: Mendel's Pea Experiment

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  1. Introduction to Genetics Mendel and Traits

  2. Genetics is the study of heredity!

  3. Gregor Mendel • Grew up in small region of Austria that is now part of the Czech Republic • Many remember him as an Austrian monk

  4. Gregor Mendel • What did he do? • Bred pea plants to study inheritance • Why is his work important? • He discovered the basic principles of heredity • Father of Genetics!

  5. Mendel’s Pea Experiment:Why Peas? 1. Many varieties w/ examinable traits 2. Was able to have strict control over how the pea plants mated 3. Peas plants had many “either/ or” characteristics that could be examined

  6. What is a trait? What is a Trait? - Specific characteristic such as seed color or pod color in a pea plant.

  7. Seven Traits Examined by Mendel

  8. 7 Traits Examined by Mendel Plant Height Seed Shape Seed Color Seed Coat Color Pod Shape Pod Color Flower Position

  9. Genes vs. Alleles • Genes: Location of a specific trait on a chromosome • Alleles: alternate forms of a gene with a slight difference in base sequence (A vs. a)

  10. Dominant vs. Recessive • Dominant: • In a pair of alleles, when one allele is stronger than the other • This allele is expressed- the one that you can “see” • Recessive: • Weaker allele in a pair of alleles • The allele that is hidden • Example: The allele for tall pea plants (T) is dominant over short pea plants (t)

  11. Genotype vs. Phenotype • Genotype = genetic makeup of an individual (think “gene = genotype”) • Example: the genotype for a pure tall pea plant would be TT • Phenotype = the expression of the genotype or the physical characteristics that you can see (think “physical = phenotype”) • Example: If the genotype for height in a pea plant is tt, then you will see a short pea plant.

  12. Homozygous vs. Heterozygous • Homozygous • when both alleles in a pair are the same • think “homo = same” • also considered to be “pure” • Example: A pure tall pea plant is homozygous dominant • Genotype = TT • Heterozygous • when the alleles in a pair are different from each other (think “hetero = different”) • Example: Tall pea plant with genotype = Tt

  13. Trait Alleles Seed Shape Round (R ___) Wrinkled (rr) Seed Color Yellow (Y ___) Green (yy) Seed coat color Gray (W ___) White (ww) Pod Shape Smooth (S ___) Wrinkled (ss) Pod Color Green (G ___) Yellow (gg) Flower Position Axial (A ___) Terminal (aa) Plant Height Tall (T ___) Short (tt) Genetics Practice: Determining Genotypes and Phenotypes • What is the genotype of a heterozygous axial plant? ______________ • What is the genotype of a wrinkled, short pea plant? ______________ • What is the genotype of a purebred green pod plant? ______________ • What is the phenotype for a ss plant? __________________________ • What is the phenotype for a Aa plant? __________________________

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