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GENETICS

GENETICS. Why do you look like that?!?. A little background…. Gregor Mendel- “Father of Genetics” Austrian monk and biologist in the mid-1800s Used pea plants to figure out how traits were inherited (passed down). Vocabulary. Genetics : the study of heredity, or how genes are inherited.

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GENETICS

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  1. GENETICS Why do you look like that?!?

  2. A little background… • Gregor Mendel- “Father of Genetics” • Austrian monk and biologist in the mid-1800s • Used pea plants to figure out how traits were inherited (passed down)

  3. Vocabulary Genetics: the study of heredity, or how genes are inherited

  4. Allele: variation of a trait; form of a gene ex. Trait- pod color / Alleles- yellow, green

  5. Dominant: allele that can mask the other (uppercase letters- A) • Recessive: allele that can be masked by the other (lowercase letters- a)

  6. Homozygous: both alleles in the pair are the same (AA or aa) • Heterozygous: both alleles in the pair are different (Aa)

  7. Genotype: genetic make-up (the genes) of an organism Ex. Uu or UU • Phenotype: physical appearance expressed by the genes Ex. Unibrow

  8. G – green pea pods g – yellow pea pods (Dominant) (Recessive) Genotypes  GG Gg gg Terms  Phenotypes  Homozygous dominant Heterozygous Homozygous recessive Green pea pods Green pea pods Yellow pea pods

  9. Mendel’s Work

  10. Laws of Heredity • Law of Segregation: Two alleles for a trait separate during gamete formation

  11. Laws of Heredity • Law of Independent Assortment: • Alleles from different genes separate independently of one another during gamete formation

  12. Punnett Squares • Used to figure out the possible genotypes and phenotypes (ratios) • Monohybrid cross: one trait of an individual is crossed with the same trait of another individual

  13. Monohybrid Cross Example Let’s look at pea pod color: • Green is dominant (G) and yellow is recessive (g) • Example: Homozygous dominant (GG) crossed with homozygous recessive (gg) G G Genotype ratio 4 Gg: 0 GG: 0 gg 100% Gg g Gg Gg Phenotype ratio 4 green: 0 yellow 100% green g Gg Gg

  14. Punnett Squares • Dihybrid cross: two traits of an individual are crossed with the same two traits of another individual

  15. Dihybrid Cross Example Must find all possible allele combinations: Traits - seed shape and seed color Alleles: R = Round r = Wrinkled Y = Yellow y = green Female: RrYy Male: RrYy both are round and yellow All combinations for each: Female: RY, Ry, rY, ry Male: RY, Ry, rY, ry

  16. Dihybrid Cross Example Cross these combinations to find possible genotypes/phenotypes of offspring: RY Ry rY ry RY RRYY RRYy RrYY RrYy Ry RRYy RRyy RrYy Rryy rY RrYY RrYy rrYY rrYy ry RrYy Rryy rrYy rryy

  17. Dihybrid Cross Example Cross these combinations to find possible genotypes/phenotypes of offspring: Genotype ratio: RRYY 1/16 RRYy 2/16 RrYY 2/16 RrYy 4/16 Rryy 1/16 Rryy 2/16 rrYY 1/16 rrYy 2/16 rryy 1/16 Phenotype ratio: Round and Yellow 9/16 Round and Green 3/16 Wrinkled and Yellow 3/16 Wrinkled and Green 1/16

  18. Types of Dominance: • 1) Complete Dominance- One allele can completely mask another RR- RedRr- Redrr- white

  19. Types of Dominance • Incomplete Dominance: one allele is partially covered by another RR- REDRR’- PINKR’R’- WHITE

  20. Types of Dominance • Co-dominance: Both alleles are dominant, so they both show through RR- REDRW- Red & WhiteWW- White

  21. Types of Dominance • 4) Multiple Alleles- when a trait has more than two alleles • Ex. Blood Type • IA- Type A • IB- Type B • i- Type O • Both complete and co-dominance are shown in creating phenotypes • Type A- IAIA, IAi • Type B- IBIB, IBi • Type AB- IAIB • Type O- ii

  22. Types of Dominance 5) Sex-linked- Allele for trait is found on a sex chromosome • Ex. Hemophilia • Normal- XH • Hemophilia- Xh • Nothing at all- Y

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