mendelian-genetics-punnett-square.pptx01 no

Biology

1. punnett square General biology 2 jessa lyn l. pananggilan

2. objectives differentiate between monohybrid and dihybrid cross objective 1 explain how probability is related to inheritance objective 2 Solve and predict Mendelian phenotypic and genotypic expression of traits in a monohybrid and dihybrid cross objective 3

3. review Who is Gregor Mendel? What are the laws of inheritance proposed by Mendel? What is the difference between phenotype and genotype?

4. What is Genetics? Genetics is the scientific study of heredity

5. What is a Trait? A trait is a specific characteristic that varies from one individual to another. Examples: Brown hair, blue eyes, tall, curly

6. What is an Allele? Alleles are the different possibilities for a given trait. Every trait has at least two alleles (one from the mother and one from the father) Example: Eye color – Brown, blue, green, hazel Examples of Alleles : A = Brown Eyes a = Blue Eyes B = Green Eyes b = Hazel Eyes

7. What are Genes? Genes are the sequence of DNA that codes for a protein and thus determines a trait.

8. Gregor Mendel Father of Genetics 1 st important studies of heredity Identified specific traits in the garden pea and studied them from one generation to another

9. Mendel’s Conclusions Law of Segregation – Two alleles for each trait separate when gametes form; Parents pass only one allele for each trait to each offspring Law of Independent Assortment – Genes for different traits are inherited independently of each other

10. Dominant vs. Recessive Dominant - Masks the other trait; the trait that shows if present Represented by a capital letter Recessive – An organism with a recessive allele for a particular trait will only exhibit that trait when the dominant allele is not present; Will only show if both alleles are present Represented by a lower case letter R r

11. Dominant & Recessive Practice TT - Represent offspring with straight hair Tt - Represent offspring with straight hair tt - Represents offspring with curly hair T – straight hair t - curly hair

12. Genotype vs. Phenotype Genotype – The genetic makeup of an organism; The gene (or allele) combination an organism has. Example : Tt, ss, GG, Ww Phenotype – The ph ysical characteristics of an organism; The way an organism looks Example : Curly hair, straight hair, blue eyes, tall, green

13. Homozygous vs. Heterozygous Homozygous – Term used to refer to an organism that has two identical alleles for a particular trait ( TT or tt ) Heterozygous - Term used to refer to an organism that has two different alleles for the same trait ( Tt ) RR Rr rr

14. Punnett Squares Punnett Square – Diagram showing the gene combinations that might result from a genetic cross Used to calculate the probability of inheriting a particular trait Probability – The chance that a given event will occur

15. Punnett Square Parent Parent Offspring

16. How to Complete a Punnett Square

17. Y-Yellow y-white Genotype: 1:2:1 (YY:Yy:yy) Phenotype : 3 Yellow 1 White

18. You Try It Now! Give the genotype and phenotype for the following cross: TT x tt (T = Tall and t = Short)

19. TT x tt Step One : Set Up Punnett Square (put one parent on the top and the other along the side) T T t t

20. TT x tt Step Two : Complete the Punnett Square T T t t Tt Tt Tt Tt

21. TT x tt Step Three : Write the genotype and phenotype T T t t Tt Tt Tt Tt Genotype: 4 - Tt Phenotype: 100% Tall Remember: Each box is 25%

22. You Try It Now! Give the genotype and phenotype for the following cross: Tt x tt

23. Tt x tt Step One : Set Up Punnett Square (put one parent on the top and the other along the side) T t t t

24. Tt x tt Step Two : Complete the Punnett Square T t t t Tt tt Tt tt

25. Tt x tt Step Two : Complete the Punnett Square T t t t Tt tt Tt tt Genotype: Tt - 2 (50%) tt - 2 (50%) Phenotype: 50% Tall 50% Short Remember: Each box is 25%

26. Some Terminology P 1 – Original parents F 1 – First generation F 2 – Second generation P 1 X P 1 = F 1 F 1 X F 1 = F 2

27. Long eyelashes (E) are dominant to short eyelashes (e). 1. What is the trait in this scenario? What are the two alleles in this scenario? A woman is homozygous recessive . What is her genotype ? A man is homozygous dominant . What is his phenotype ? A man is heterozygous for eyelashes. What is his genotype . A woman’s genotype is EE. What is her phenotype ? A cross occurs between a homozygous recessive male and a heterozygous woman …. What percent chance will their first child have long eyelashes? What percent chance will their 8 th child have long eyelashes? HINT…DRAW A PUNNETT SQUARE!

28. Long eyelashes (E) are dominant to short eyelashes (e). What is the trait in this scenario? Eyelash Length

29. Long eyelashes (E) are dominant to short eyelashes (e). What are the two alleles in this scenario? E and e OR Long and short eyelashes

30. Long eyelashes (E) are dominant to short eyelashes (e). 3. A woman is homozygous recessive . What is her genotype ? ee

31. Long eyelashes (E) are dominant to short eyelashes (e). A man is homozygous dominant . What is his phenotype ? Long eyelashes

32. Long eyelashes (E) are dominant to short eyelashes (e). A man is heterozygous for eyelashes. What is his genotype ? Ee

33. Long eyelashes (E) are dominant to short eyelashes (e). A woman’s genotype is EE. What is her phenotype ? Long Eyelashes

34. Long eyelashes (E) are dominant to short eyelashes (e). A cross occurs between a homozygous recessive male and a heterozygous woman …. Male – ee Female - Ee

35. Long eyelashes (E) are dominant to short eyelashes (e). 7. A cross occurs between a homozygous recessive male and a heterozygous woman …. Ee Ee ee ee e e E e

36. Long eyelashes (E) are dominant to short eyelashes (e). What percent chance will their first child have long eyelashes? What percent chance will their 8 th child have long eyelashes? 50% 50%

37. Dihybrid Punnett Squares What exactly is a dihybrid cross? Predicting the outcomes from crossing 2 traits. Why do we use them? Instead of doing to monohybrid crosses, you can combine them to see all the possible combinations from that particular mother and father.

38. Dihybrid Cross Traits: Seed shape & Seed color Alleles: R round r wrinkled Y yellow y green RrYy x RrYy RY Ry rY ry RY Ry rY ry All possible gamete combinations

39. Dihybrid Cross RY Ry rY ry RY Ry rY ry

40. Dihybrid Cross RRYY RRYy RrYY RrYy RRYy RRyy RrYy Rryy RrYY RrYy rrYY rrYy RrYy Rryy rrYy rryy Round/Yellow: 9 Round/green: 3 wrinkled/Yellow: 3 wrinkled/green: 1 9:3:3:1 phenotypic ratio RY Ry rY ry RY Ry rY ry

41. Dihybrid Cross : a cross that shows the possible offspring for two traits 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 Trait one Trait Two

42. Dihybrid Cross BbRr x BbRr Step 1 : Find ALL possible gametes that can be made from each parent. Remember, each gamete must have one B and one R. DAD MOM

43. Foil BbRr BR Br bR br

44. Practice What are the possible gametes for BBrr Br Br Br Br

45. Practice What are the possible gametes for HhTT? HT HT hT hT

46. Dihybrid Cross BbRr x BbRr Possible gametes: BR Br bR br DAD MOM F O I L

47. Dihybrid Cross BbRr x BbRr DAD MOM Step 2 : Arrange all possible gametes for dad on the top of your Punnett Square, and mom down the side

48. 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 Step 3 : Fill in the Punnett Square (find the possible genotypes of the offspring) B B B B B B B B b b b b b b b b B B B B B B B B b b b b b b b b R R R R r r r r R R R R r r r r R R R R r r r r R R R R r r r r

49. Dihybrid Crosses Fur Color: B: Black b: White Coat Texture: R: Rough r: Smooth BbRr x BbRr BR bR br bR Br BR br Br BBRR BbRR BbRr BBRr BBrr BbRr Bbrr BbRR BbRr bbRR bbRr BbRr Bbrr bbRr bbrr BBRr

50. BR bR br bR Br BR br Br BBRR BbRR BbRr BBRr BBrr BbRr Bbrr BbRR BbRr bbRR bbRr BbRr Bbrr bbRr bbrr 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

51. BR bR br bR Br BR br Br BBRR BbRR BbRr BBRr BBrr BbRr Bbrr BbRR BbRr bbRR bbRr BbRr Bbrr bbRr bbrr 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

52. Practice in your notes… In pea plants, yellow seeds (Y) are dominant over green seeds (y), and rounded peas (R) are dominant over wrinkled peas (r). Cross ( what do you have to draw?) 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.

53. YyRr X yyrr YR yR yr yr yr yr yr Yr YyRr yyRr yyrr YyRr Yyrr yyRr yyrr YyRr Yyrr yyRr yyrr YyRr Yyrr yyRr yyrr Yyrr