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Genetics & Heredity

This lesson delves into the fundamentals of genetics and heredity, emphasizing Gregor Mendel's pivotal experiments with pea plants. Students will explore how biological traits—such as seed shape, plant height, and flower color—are inherited across generations. Key concepts include dominant vs. recessive traits and the significance of genes and alleles. The 3:1 ratio of dominant to recessive traits observed by Mendel is highlighted, along with explanations of genotypes and phenotypes. Punnett squares are introduced as a useful tool for predicting offspring traits.

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Genetics & Heredity

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  1. Genetics & Heredity S7L3 Students will recognize how biological traits are passed on to successive generations.

  2. Gregor Mendel • Father of Genetics • Austrian monk • Studied pea plant inheritance • Traits: seed shape, plant height, flower color, etc.

  3. Mendel’s Experiment

  4. Mendel’s Experiment

  5. Mendel’s Experiment

  6. So what happened???

  7. Dominant vs Recessive • Observed in the first generation • “Covers over” the recessive trait • Disappears in first generation • Reappears in second generation Dominant Trait Recessive Trait

  8. Mendel’s Results • For every 3 dominant traits, 1 recessive trait • Ratio 3:1

  9. Genes & Alleles • GENE: segment of DNA that gives instructions for an inherited trait • Each parent gives one set of genes to the offspring. • The different forms of a genes are called ALLELES.

  10. About alleles… • One from each parent; two per trait • Either dominant (capital letter) or recessive (lowercase letter) Brown Eyes Blue Eyes Dominant  BB or Bb Recessive bb

  11. About alleles… Blue eyes are represented by bb • “bb” is the genotype (genetic makeup) • “blue” is the phenotype (physical appearance) Brown eyes is shown as BB or Bb • “BB” or “Bb” are genotypes • “brown” is the phenotype

  12. About alleles… • If both letters of the genotype are the same, it is called HOMOZYGOUS. BB or bb • If the letters of the genotype are different, it is called HETEROZYGOUS. Bb

  13. Homozygous… • If the alleles are the same, the organism is called pure-breeding.

  14. Heterozygous… • If the alleles are different, the organism is a hybrid.

  15. Punnett Squares • Used to view the possible combination of offspring from particular parents. • Parent’s genes go outside the box • Offsprings’ genes go inside the box B B b b

  16. Punnett Square in Action!!!

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