1. Mendel’s Laws of Heredity – Chp 10.1 Why we look the way we look...

2. What is heredity? b The passing on of characteristics (traits) from parents to offspring b Genetics is the study of heredity

3. Who was Gregor Mendel? (1822-1884) b Considered the Father of Heredity b Monk who first discovered that there are RULES or LAWS governing how traits are passed from parents to offspring b He crossed 1000’s of pea plants over many years to make his discovery

4. Traits Mendel Studied:

5. Crossing Pea Plants: b Fertilization - the uniting of male and female gametes b Cross - combining gametes from parents with different traits (TT x tt) P1 = parent generationP1 = parent generation F1 = 1st offspring generationF1 = 1st offspring generation F2 = 2nd offspring generationF2 = 2nd offspring generation

7. Part 2: Mendel’s Rules & Laws

8. 1) Rule of Unit Factors b Each organism has two alleles for each trait –Alleles - different forms of the same gene –Genes - located on chromosomes, they control how an organism develops

9. 2) Rule of Dominance b The trait that is observed in the offspring is the dominant trait (uppercase) b The trait that disappears in the offspring is the recessive trait (lowercase)

10. Dominant and Recessive b Observed trait is dominant B = brown hairB = brown hair R = can roll tongueR = can roll tongue T = tallT = tall b Hidden trait = recessive b = red hairb = red hair r = can’t roll tonguer = can’t roll tongue t = shortt = short

11. Phenotype & Genotype b Phenotype - the way an organism looks –red hair or brown hair b genotype - the gene combination of an organism –AA or Aa or aa

12. Heterozygous & Homozygous b Heterozygous - if the two alleles for a trait are different (Aa) b Homozygous - if the two alleles for a trait are the same (AA or aa) Homozygous dominant = AAHomozygous dominant = AA Homozygous recessive = aaHomozygous recessive = aa

13. 3) Law of Segregation b The two alleles for a trait must separate when gametes are formed b A parent randomly passes only one allele for each trait to each offspring

14. Law of Segregation explained b During Meiosis – homologous chromosomes and their alleles separate. N = normal skin n = albino B = brown eyes b = blue eyes N n B b n B n b N b NBNB Parent cell - diploid Gamete possibilities - haploid

15. 4) Law of Independent Assortment b The genes for different traits are inherited independently of each other. b Just because you get Dad’s blue eyes doesn’t mean you will get his blonde hair also!

16. Monohybrid Cross Monohybrid Cross - crossing parents who differ in only one trait (TT, Tt, tt) - Use a special method called punnet squares.

17. Questions... 1) How many does alleles does an individual receive for each trait?

18. 2)What is an allele? 3)How many alleles does a parent pass on to each offspring for each trait?

19. 4) What are the gametes of the following parents? a) Aab) ggc) RR

20. 5) What do we call the trait that is observed? What case (upper or lower) is it written in?

21. 6) What about the one that disappears? What case is it written in?

22. 7) What is the difference between phenotype and genotype?

23. 8) If green peas (G) are dominant over yellow peas (g), give the phenotypes for the following genotypes: a) GGb) Ggc) gg

24. 9) What is the difference between homozygous and heterozygous?

25. 10) Round peas (R) are dominant over wrinkled peas (r). Give the genotypes for the following phenotypes: a)Round b)Wrinkled