1. Characteristics of Living Things Living things are made up of cells Unicellular – one celled organisms Multicellular – many celled organisms Remember/Review

2. Characteristics of Living Things Living things reproduce to make offspring of the same species Sexual reproduction Asexual reproduction

3. Living things grow and develop Characteristics of Living Things

4. 1.What type of cell division is the diagram above?

5. Chromosome Number in Body Cells vs. Gametes Body Cells Diploid (2n) - have 2 sets Gametes Haploid (n) - have 1 set

6. Meiosis

7. Meiosis is Reduction Division Chromosome number is cut in half by separation of homologous chromosomes in diploid cells

8. Crossing Over Occurs in Prophase I Results in variations in daughter cells

9. Crossing-Over & Gene Mapping Farther apart 2 genes are, more likely they’ll be separated Frequency of crossing-over is equal to the distance between 2 genes

10. How close are 2 usually independently assorted genes? Really far…

11. Summarize the Events of Meiosis

12. Events of Meiosis

13. Results of Meiosis 4 haploid (n) cells Genetically different from each other & the original cell

14. Differences Between Mitosis & Meiosis MITOSIS produces 2 identical diploid (2n) cells MEIOSIS produces 4 different haploid (n) cells

15. Human Cells 2n=46. Sperm Cell – 23 chromosomes – Gamete is haploid (n) Egg Cell – 23 chromosomes – Gamete is haploid (n) White Blood Cell – 46 chromosomes – Body cell is diploid (2n)

17. Independent Assortment Applied to Chromosomes The “chromosomes” sort independently, not as individual “genes”

19. Introduction to Genetics Genetics = the study of heredity

21. Gregor Mendel – The Father of Genetics – carried out important studies of heredity Heredity—the passing on of traits from parents to offspring He studied pea plants

22. Trait- a specific characteristic that is controlled by genes – Exp. Eye color, hair color, height

23. Chromosomes – Tightly coiled DNA where your genes are carried Genes – Sections of DNA that control your traits

24. Homologous Chromosomes – Chromosomes that are the same size and shape and carry the same genes. You get one from your mother and one from your father that match up. Short pea plant Tall pea plant All tall pea plants 3 tall: 1 short P1P1 F1F1 F2F2

25. – Alleles – The different forms a gene can take. (Letters) 2 Types of Alleles: – 1. Dominant - Represented by a capital letter » (Exp. A) – 2. Recessive - Represented by a lower-case letter (Exp. a)

26. – Genotype The combination of two alleles (letters) that represent the genetic make-up of an individual. (AA, Aa, aa) – Phenotype The observable physical characteristic of an individual that are the result of its genotype. (Long eyelashes, Blue or Brown eyes)

27. 3 Types of Genotypes: 1. Homozygous Dominant – 2 identical alleles that are capitalized (AA, TT) 2. Heterozygous – 2 different alleles (Aa, Tt) 3. Homozygous Recessive – 2 identical alleles that are lower-case (aa, tt)

28. Principle of Dominance An organism with a recessive allele for a particular trait will exhibit that form only when the dominant allele for the trait is not present. Organisms with a heterozygous genotype (Aa) will never exhibit the recessive trait because it is hidden (masked) by a dominant allele.

30. You try this one: AA A a

32. Dihybrid Cross: a cross that shows the possible offspring for two traits 16 squares Fur Color: B: Black b: White Coat Texture: R: Rough r: Smooth In this example, we will cross a heterozygous individual with another heterozygous individual. Their genotypes will be: BbRr x BbRr

33. Dihybrid Cross BbRr x BbRr First, you must find ALL possible gametes that can be made from each parent. Remember, each gamete must have one B and one R.

34. Dihybrid Cross BbRr x BbRr Possible gametes: BR Br bR br Next, arrange all possible gametes for one parent along the top of your Punnett Square, and all possible gametes for the other parent down the side of your Punnett Square…

35. Dihybrid Crosses: a cross that shows the possible offspring for two traits Fur Color: B: Black b: White Coat Texture: R: Rough r: Smooth BbRr x BbRr BR bR br bR Br BR br Br Then, find the possible genotypes and phenotypes of the offspring

36. Dihybrid Crosses: a cross that shows the possible offspring for two traits Fur Color: B: Black b: White Coat Texture: R: Rough r: Smooth BbRr x BbRr BR bR br bR Br BR br Br BBRRBbRRBbRr BBRrBBrrBbRrBbrr BbRRBbRrbbRRbbRr BbRrBbrrbbRrbbrr BBRr

37. BR bR br bR Br BR br Br BBRRBbRRBbRr BBRrBBrrBbRrBbrr BbRRBbRrbbRRbbRr BbRrBbrrbbRrbbrr BBRr How many of the offspring would have a black, rough coat? How many of the offspring would have a black, smooth coat? How many of the offspring would have a white, rough coat? How many of the offspring would have a white, smooth coat? Fur Color: B: Black b: White Coat Texture: R: Rough r: Smooth

38. BR bR br bR Br BR br Br BBRRBbRRBbRr BBRrBBrrBbRrBbrr BbRRBbRrbbRRbbRr BbRrBbrrbbRrbbrr BBRr How many of the offspring would have black, rough coat? How many of the offspring would have a black, smooth coat? How many of the offspring would have a white, rough coat? How many of the offspring would have a white, smooth coat? Fur Color: B: Black b: White Coat Texture: R: Rough r: Smooth Phenotypic Ratio 9:3:3:1

39. More Practice… In the space provided in your notes work the following dihybrid problems In pea plants, yellow seeds (Y) are dominant over green seeds (y), and rounded peas (R) are dominant over wrinkled peas (r). Cross a plant that is heterozygous for both traits with a plant that is homozygous recessive for both traits. Draw a Punnett square to show all possible offspring, and determine the genotypic and phenotypic ratios.

40. YyRr X yyrr YR yR yr Yr YyRryyRryyrr YyRrYyrryyRryyrr YyRrYyrryyRryyrr YyRrYyrryyRryyrr Yyrr

41. Section 1 Check Question 1 The passing on of characteristics from parents to offspring is __________. D. allelic frequency C. pollination B. heredity A. genetics

42. Section 1 Check Question 2 What are traits? Answer A specific characteristic that is controlled by genes. Height, hair color and eye color are examples of traits in humans.

43. Section 1 Check Question 3 Gametes are __________. D. fertilized cells that develop into adult organisms C. both male and female sex cells B. female sex cells A. male sex cells

44. Section 1 Check Question 4 Which of the following genotypes represents a animal that is homozygous dominant for a trait? a. KK b. Kk c. kk

45. Section 1 Check Question 5 Which of the following genotypes represents a plant that is homozygous recessive for height? C. tt B. Tt A. TT

46. Mendelian Exceptions - Not all genes show simple patterns of dominant and recessive alleles Because the majority of traits are controlled by more than one gene/alleles There are some exceptions to Mendel’s Laws.

47. 1. INCOMPLETE DOMINANCE Neither allele is completely dominant Both alleles combine equally to give a new trait. Called hybrids EX: red flower (RR) crossed with white flower (R’R’) produces pink flower (RR’)

48. In snapdragons, the combined expression of both alleles for flower color produces a new phenotype that is pink. This illustrates incomplete dominance. The Punnett square above shows that both the white and red snapdragons are homozygous. Which of the following would be the correct product from a cross between two heterozygous pink snapdragons? [VA05 EOC] – A 1 red, 2 pink, 1 white – B 2 red, 2 white – C 2 red, 1 pink, 1 white – D 1 red, 1 pink, 2 white

49. 2. CODOMINANCE Both alleles are expressed EX: cross a black chicken with a white chicken, offspring will be black and white checkered. Roan cow (RW) Red cow (RR)White cow (WW)

50. In a certain cactus, prickly spines can be two pronged or one pronged. If a true breeding (homozygous) one- pronged cactus is crossed with a true breeding two- pronged cactus, the F1 generation has a mixture of spines, some are two-pronged, some are one-pronged. Is this an example of codominance or incomplete dominance? codominance Practice Problems

51. MULTIPLE ALLELES : more than two alleles control a phenotype Ex: blood type Genotypes: AO- 2/4 or 50% OO- 2/4 or 50% Phenotypes: Type A- 2/4 or 50% Type O- 2/4 or 50%

52. Blood type inheritance Blood type = presence or absence of proteins on red blood cells Usually have to do more than one punnett square to determine possibilities for kids. Phenotypes Blood types Genotypes Alleles for blood type A AA or AO B BB or BO AB Only AB O Only OO

53. Section 12.2 Summary – pages 315 - 322 Traits controlled by genes located on sex chromosomes are called sex-linked traits. The alleles for sex-linked traits are written as superscripts of the X or Y chromosomes. Sex-linked inheritance

54. Section 12.2 Summary – pages 315 - 322 Sex Determination If you are female, your 23 rd pair of chromosomes are homologous, XX. If you are male, your 23 rd pair of chromosomes XY, look different. XX Female YX Male XX Female XY Male X X XY XX Female XY Male XX Female XY Male

55. Sex Linked Traits When genes are located on the X chromosome, females receive two alleles for these genes, but males only receive one. In males, the genotype is automatically known. – Colorblind male - X c Y (recessive) – Normal male - X C Y (dominate). A female can be: – X C X C - normal – X C X c - carrier – X c X c - colorblind

56. Males can pass it to all of their daughters, none to sons Females have 50/50 chance of passing it to all of their children Ex: – Hemophilia- can’t clot blood – Colorblindness- can’t see certain colors.

57. 4. SEX-LINKED TRAITS: controlled by genes located on sex chromosomes Usually carried on X chromosome Since females are XX, they are usually carriers of the trait Since males are Xy, they have one big & one small, stumpy chromosome. The small chromosome (y) does not carry an allele so whatever allele is on the X (donated by mom) is what the boy will have. He is either completely dominant or completely recessive Boys cannot be a carriers of a sex linked trait.

58. 5. Polygenic inheritance-2 or more genes affect the phenotype. Ex: height, weight, skin color, eye color Heterochromia- uneven distribution of pigment resulting from disease or injury