Gregor Mendel “ Father of Genetics ” Wrote “Experiments in Plant Hybridization” in 1865

1. Gregor Mendel • “Father of Genetics” • Wrote “Experiments in • Plant Hybridization” in 1865 • His work wasn’t discovered • until the next century

2. Painting of Mendel

3. Mendel

4. Table 14.1 The Results of Mendel’s F1 Crosses for Seven Characters in Pea Plants

6. Sweet Pea Flowers

7. Alleles, Alternative Versions of a Gene

8. Homozygous means having only one form of gene or allele Ex: WW or ww

9. Heterozygous means a trait represented by at least two different alleles, or forms of a gene Ex: Ww

10. In the formation of a zygote, or fertilized egg, each parent of an organism contributes one form of a gene or allele, for each trait in most cases.

11. In Mendelian Genetics, dominant traits are represented by capital letters; recessive ones by lower case letters

12. Dominant traits (genes) are always expressed if the gene is present; recessive traits are expressed only if the dominant genes are absent

13. For example, widow’s peak (W) is a dominant trait in humans. If the gene for widow’s peak is present, W, the person will have widow’s Peak. (WW, Ww)

14. eye color locus B = brown eyes eye color locus b = blue eyes Paternal Maternal Homologous Chromosomes This person would have brown eyes (Bb)

15. B sperm B B Bb haploid (n) b b diploid (2n) b meiosis II meiosis I Meiosis - eye color

16. The physical appearance of an organism is known as the phenotype; the genetic makeup (the letters) are known as the genotype Ex: Widow’s peak is the pheno- type; Ww is the genotype

18. The way to show the pos- sible pairings of genes between two organisms is called a Punnett Square.

19. Punnett Square • A Punnett square is used to show the possible combinations of gametes.

20. T T t t Breed theP generation • tall (TT) vs. dwarf (tt) pea plants

21. T T produces the F1 generation Tt Tt t Tt Tt t All Tt = tall (heterozygous tall) tall (TT) vs. dwarf (tt) pea plants

22. Breed theF1 generation • Heterozygous Tall (Tt) pea plants T t T t

23. Cross a purebred black guinea pig and a purebred brown guinea pig. Black is dominant over brown.

24. B B (black) Bb Bb b All offspringare black and heterozygous. Bb Bb b (Brown)

25. If bushy eyebrows (B) are dominant over fine eyebrows, (b), show the cross between one parent heterozygous for the trait and one who is homozygous recessive.

26. What are the phenotypes and genotypes of the offspring? Answer: Bushy (Bb) 50% and fine (bb) 50%

27. Monohybrid Cross • A breeding experiment that tracks the inheritance of a single trait. Dihybrid Cross • A breeding experiment that tracks • the inheritance of two traits.

28. Mendel’s “principle of segregation” a. pairs of genes on homologous chromosomes separate during gamete formation (meiosis) and end up in different gametes. b. the fusion of gametes at fertilization pairs genes once again. Ex: The alleles for height in Mendel’s pea plants end up in separate gametes. Tt X Tt could yield four the offspring: TT, Tt, Tt, tt.

29. Meiosis - eye color B sperm B B Bb haploid (n) b b diploid (2n) b meiosis II meiosis I

30. Mendel’s Law of Segregation

31. Mendel’s “principle of independent assortment” (2 different genes) a. each pair of alleles on nonhomologous chromosomes segregates independently of other pairs during gamete formation Ex: When Mendel crossed F1 plants that were heterozygous for round yellow peas, some F2 plants did not resemble the parent plants.

32. Independent Assortment • How many different gametes can be produced for the following allele arrangements? • Remember: 2n (n = # of heterozygotes) 1. RrYy 2. AaBbCCDd 3. MmNnOoPPQQRrssTtUu

33. Answers: 1. RrYy: 2n = 22 = 4 gametes RY Ry rY ry 2. AaBbCCDd: 2n = 23 = 8 gametes ABCD ABCd AbCD AbCd aBCD aBCd abCD abCD 3. MmNnOoPPQQRrssTtUu: 2n = 26 = 64 gametes

34. Autosomal Inherited Traits are inherited via the autosomes (non-sex) chromosomes. How many autosomes are in each of your somatic cells?

35. That’s right! There are 44 autosomes and 2 sex chro- mosomes in each of your somatic (non-sex) cells.

36. Figure 13.x5 Human male karyotype shown by bright field G-banding of chromosomes

37. Autosomal Inherited • Genetic Disorders • include: • Cystic Fibrosis • Tay-Sachs Disease • Sickle Cell Anemia • Huntington Disease (this • one is dominant!)

38. Testing a Fetus for Genetic Disorders

40. Cystic Fibrosis • Most common inherited fatal disorder in the U.S. • Median age of death–37 • One in every 29 Americans has the gene • Mucus builds up in the lungs

41. Francis Collins, current director of the National Human Genome Research Institute (NHGRI) helped pioneer the discovery of the CF gene in 1989.

42. Francis Collins, discoverer of the Cystic Fibrosis Gene

43. Former NFL Quarterback, Boomer Esiason and his son, Gunnar, who has CF.

45. Diagnosis:Treatment:

47. If a man who does not have Cystic Fibrosis has a sister who died of CF. He marries a woman who does not have the disease or any history of it in her family, what is the probability that they will have kids with the disease?

48. Tay Sachs Diseasea lipid-digesting enzyme is defective in lysosomes

49. If two parents are each carriers of the gene for Tay-Sachs Disease, what is the probability of them having a child with the disease?

50. That’s right! They have a 25% chance! t T Tt TT T Homozygous Dominant Heterozygous tt Tt t Homozygous Recessive