Genetics & Heredity

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!!!