Genetics

1. Genetics Why do we look the way we do? Honors Biology Chapters 9 & 12

2. Inheritance of chromosomes • Egg + sperm  zygote egg meiosis zygote mitosis &development fertilization sperm

3. Inheritance of genes • Chromosomes passed from Mom & Dad to offspring are comprised of genes • may be same information • may be different information eye color (blue or brown?) eye color (blue or brown?)

4. Effect of genes • Gene = region of a chromosome that codes for a trait • Genes come in different versions for each trait • brown vs. blue eyes • brown vs. blonde hair • A version of a gene = an allele

5. Genes affect what you look like X bb BB Bb Bb Bb Bb Where did the blue eyes go??

6. Genes affect what you look like… X bb Bb Bb Bb bb bb Why did the blue eyes stay??

7. Genes affect what you look like… X Bb Bb bb BB or Bb BB or Bb BB or Bb Where did the blue eyes come from??

8. What did we show here? • Genes come in “versions” • brown vs. blue eye color • alleles • Alleles are inherited separately from each parent • brown & blue eye colors are separate & do not blend • either havebrown or blueeyes, not a blend • Some alleles mask others • brown eye color masked blue

9. eye color (blue?) hair color hair color How does this work? • Homologous chromosomes have same genes… • …but maybe different alleles eye color (brown?)

10. Traits are inherited as separate units • For each trait, an organism inherits 2 copies of a gene (2 alleles), 1 from each parent 1 from Mom homologous chromosomes 1 from Dad

11. Genetics vs. appearance • There can be a difference between how an organism looks & its genetics • Its expressed trait/s = phenotype • brown eyes vs. blue eyes • Its alleles, or genetic makeup = genotype • BB, Bb, bb 2 people can have the same phenotype but have different genotypes: BB vs Bb

12. B B B b BB Bb Genetics vs. appearance How were these brown eyes made? eye color (brown) eye color (brown) eye color (brown) eye color (blue) vs.

13. Practice If G is the allele forpointy ears and g is the allele for floppy ears, what will be the ear shape phenotypes of the puppies with these genotypes? The dominant allele is _ for the trait ___________ The recessive allele is _ for the trait ___________ Genotype GG = Phenotype __________ Genotype Gg = Phenotype __________ Genotype gg = Phenotype ___________

14. Practice G is for pointy ears and g is for floppy ears. Also, H is for a pink nose and h is for a black nose. Genotype GGHH = Phenotype ______ and ______ Genotype GgHh = Phenotype ______ and ______ Genotype gghh = Phenotype ______ and _______ Genotype GGhh = Phenotype ______ and _______ Genotype Gghh = Phenotype ______ and _______ Genotype ggHH = Phenotype ______ and _______

15. Practice • Which of these are traits and which are phenotypes? • 1. Finger length • 2. Blue eyes • 3. Long hair • 4. Number of leaves • 5. Shape of tentacles • 6. Warbling song

16. Practice • Which of these are alleles and which are traits? • 1. Eye color • 2. Bone integrity • 3. i • 4. Insulin shape • 5. B • 6. Na

17. Practice • Which of these are phenotypes and which are genotypes? • 1. Curly hair • 2. Jj • 3. PP • 4. Arthritic knees • 5. Type B blood • 6. Spotted fur and a pink nose • 7. HHGg • 8. Purple leaves and spiny stem

18. Genetics&The Work of Mendel

19. Gregor Mendel • Modern genetics began in the mid-1800s in an abbey garden, where a monk named Gregor Mendel documented inheritance in peas • used good experimental design • usedmathematicalanalysis • collected data & counted them • excellent example of scientific method

20. Mendel’s work Pollen transferred from white flower to stigma of purple flower • Bred pea plants • cross-pollinate true breeding parents • allowed offspring to self-pollinate& observed next generation all purple flowers result self-pollinate ?

21. Mendel collected data for 7 pea traits

22. true-breeding purple-flower peas true-breeding white-flower peas 100% purple-flower peas 1st generation (hybrids) 100% 75% purple-flower peas 25% white-flower peas 3:1 2nd generation Looking closer at Mendel’s work X Parents F1 self-pollinate F2

23. What did Mendel’s findings mean? • Some traits mask others • purple & white flower colors are separate traits that do not blend • purple x white ≠ light purple • purplemaskedwhite • dominant allele • functional protein • affects characteristic • masks other alleles • recessive allele • no noticeable effect • allele makes a non-functioning protein allele producingfunctional protein mutant allele malfunctioningprotein homologouschromosomes

24. Mendel’s Results and Conclusions RESULT: • Whenever Mendel crossed two P plants, one of the traits disappeared in the F1 plants. • The missing trait reappeared in the F2 plants in a 3:1 ratio pattern CONCLUSION: LAW OF DOMINANCE • One trait is dominant because it masked or dominated the other trait • One trait is recessive because it “hid” behind the dominant one. It can only be seen when the plant has no dominant alleles.

25. Mendel’s Results and Conclusions • CONCLUSION: LAW OF SEGREGATION • Pairs of alleles segregate (separate) during the formation of gametes (meiosis—homologous pairs separate) • A parent only passes one allele for each gene onto a zygote

26. Mendel’s Results and Conclusions • CONCLUSION: LAW OF INDEPENDENT ASSORTMENT • Factors for different characteristics are distributed to gametes independently or randomly. • Which allele is passed for one one gene doesn’t affect which allele is passed down from other genes

27. Mendel’s Legacy • DNA and chromosomes weren’t discovered until many decades after Mendel’s death • Today, we understand the genetic mechanisms that underlie his mathematical discoveries…

28. Gamete Formation • Suppose there’s a gene for eye color, with the alleles B for brown eyes or b for blue eyes. • A man has the genotype Bb, which gives him the phenotype brown eyes. • Meiosis produces his gametes… He can make gametes that are EITHER B or b. Half of his gametes will be one, half will be the other. We simplify, saying that he produces either B or b allele sperm. Equal chance of each. b b b S Phase b b b b 1st Cytokinesis 2nd Cytokinesis B B B B Normal cell in G1 B B B Four Gametes

29. Practicing the Law of Segregation (Some gametes are written with more than one letter. If Dad’s genotype is LTLt, he will make a sperm that has the LT allele or a sperm that has the Lt allele.) Genotype YY makes what gamete/s? Genotype Tt makes what gamete/s? Genotype bb makes what gamete/s? Genotype Ii makes what gamete/s? Genotype K1K2 makes what gamete/s?

30. B B B b b b BB Bb bb How do we say it? 2 of the same allele= Homozygous BB = brown eyes bb= blues eyes homozygous dominant homozygous recessive 2 different alleles= Heterozygous Bb= brown eyes

31. Practice • Identify each of these genotypes as being homozygous or heterozygous. • GG ____________ Ss ________ • Yy ___________ Vv ________ • kk ____________

32. Practice • Identify each of these genotypes as being homozygous dominant, homozygous recessive, or heterozygous. • ee ____________ CC ________ • QQ ___________ pp ________ • Ll ____________

33. Practice • Suppose that the I allele codes for orange fins and the i allele codes for yellow fins. • The heterozygous genotype: __ • The homozygous dominant genotype: __ • The homozygous recessive genotype: __ • A fish with yellow fins must have a _____________ genotype. • A fish with orange fins could be either _____________ or ___________________.

34. B b B b Punnett squares Bb x Bb male / sperm X BB Bb female / eggs Bb bb

35. Genetics and Probability • Figuring out offspring is a matter of chance. • A Punnett Square provides the probabilities of two parents producing particular zygotes. • An example, using coins:

36. Punnett Squares • Using the letter H to stand for heads… • If you flip a coin that’s heads (H) on both sides, what are the chances that it will come up heads (H)?

37. Punnett Squares • If it’s a normal coin, heads (H) on one side and tails (h) on the other… • What are the odds that it will come up heads (H) on a flip?

38. Punnett Squares • If you flip TWO normal coins, what are the odds that you will get heads (H) on both flips?

39. Punnett Squares • The first flip will be either heads (H) or tails (h):

40. Punnett Squares • The second flip will also be either heads (H) or tails (h):

41. Punnett Squares • These are the possible combinations that you could have produced:

42. Punnett Squares • These are the possible combinations that you could have produced:

43. Punnett Squares • These are the possible combinations that you could have produced:

44. Punnett Squares • These are the possible combinations that you could have produced:

45. Punnett Squares • These are the possible combinations that he could have produced: H H H H H H

46. Punnett Squares • 1 in 4 possible outcomes would be both heads (HH). The chance of getting heads on both flips = 1/4 = 25% H h H H H H h H h h h h

47. Punnett Squares • What are the odds of getting heads on one flip, tails on the other? h H H H H H h H h h h h

48. Punnett Squares • 2 of 4 possible outcomes = 1/2 = 50% h H H H H H h H h h h h

49. Punnett Squares • What if you flip two different coins: • One coin has two heads • The other is normal, one heads and one tails • What are the odds of getting heads on both flips?

50. Punnett Squares H H • 2/4 = 1/2 = 50% • This is called a Punnett Square. • Punnett Squares display all possible gametes and possible offspring. H H H H H H h H h h