Genetics and Heredity

1. Genetics and Heredity

2. Genetics The study of heredity, how traits are passed from parent to offspring or x = or

3. The study of heredity started with the work of Gregor Mendel and his pea plant garden Mendel was an Austrian Monk that lived in the mid 1800’s

4. Inheritance Theory Prior to Mendel 1. Traits “blended” • Trait: characteristics to be passed from parent to offspring • “bloodlines”: thought traits passed through the blood 2. Problem with blending: cannot account for unexpected traits

5. Mendel noted that the size of pea plants varied. He cross-bred these pea plants to find some surprising results.

6. Steps of Mendel's Experiment

7. Mendel’s cross between tall pea plants yielded all tall pea plants. His cross between small pea plants yielded all small pea plants. X = X = Mendels’ cross between tall pea plants and small pea plants yielded all tall pea plants. x =

8. T t T TT Tt t Tt tt Here we crossed two peas which contained both tall and short information.

9. When Mendel crossed these second generation tall pea plants he ended up with 1 out 4 being small. x =

10. A cross in which only one trait is studied is called monohybrid cross .

11. 5.  Mendel named every generation: Starting generation – P (parent) generation. The following offspring generation was called F1 - first generation (daughter generation), F2 - second filial generation, and so on.

12. P F1 F2

13. Mendelian Genetics • Mendel studied a number of characteristics in pea plants including: • Height - short or TALL

14. Mendelian Genetics • Mendel studied a number of characteristics in pea plants including: • Height - short or TALL • Seed color - green or YELLOW

15. Mendelian Genetics • Mendel studied a number of characteristics in pea plants including: • Height - short or TALL • Seed color - green or YELLOW • Seed shape - wrinkled or ROUND

16. Mendelian Genetics • Mendel studied a number of characteristics in pea plants including: • Height - short or TALL • Seed color - green or YELLOW • Seed shape - wrinkled or ROUND • Seed coat color - white or GRAY

17. Mendelian Genetics • Mendel studied a number of characteristics in pea plants including: • Height - short or TALL • Seed color - green or YELLOW • Seed shape - wrinkled or ROUND • Seed coat color - white or GRAY • Pod shape - constricted or SMOOTH

18. Mendelian Genetics • Mendel studied a number of characteristics in pea plants including: • Height - short or TALL • Seed color - green or YELLOW • Seed shape - wrinkled or ROUND • Seed coat color - white or GRAY • Pod shape - constricted or SMOOTH • Pod color - yellow or GREEN

19. Mendelian Genetics • Mendel studied a number of characteristics in pea plants including: • Height - short or TALL • Seed color - green or YELLOW • Seed shape - wrinkled or ROUND • Seed coat color - white or GRAY • Pod shape - constricted or SMOOTH • Pod color - yellow or GREEN • Flower position - terminal or AXIAL

20. Mendelian Genetics • We will work with the following three: • Height - short or TALL • Seed color - green or YELLOW • Seed shape - wrinkled or ROUND • Seed coat color - white or GRAY • Pod shape - constricted or SMOOTH • Pod color - yellow or GREEN • Flower position - terminal or AXIAL

21. Mendel’s work led him to the understanding that traits such as plant height are carried in pairs of information not by single sets of information. -Carrying the information are chromosomes. -Chromosomes are made up of sections called genes. -Genes are made up of DNA

23. DNA D.N.A. - Deoxyribonucleic Acid Molecule made of: 1. Deoxy Sugar 2. Combination of four nitrogen bases Either: a. Guanine b. Cytocine c. Thymine d. Adenine The sum total of combinations that these four bases are capable of creating are greater than all the stars visible in the night time sky

24. DNA • Nitrogen bases pair up • Cytosine & Guanine • Thymine & Adenine • Pairing creates a ladder shape • Angle of bonds creates a twist Ladder and Twist produces the famous “Double Helix”

25. DNA Nucleus Cell • DNA resides in all cells • Inside the nucleus • Each strand forms a chromosome DNA

26. DNA DNA is found in all living cells • It controls all functions inside a cell • It stores all the genetic information for an entire living organism • Single cell like an amoeba • Multi cell like a human

27. Genetics Small sections of DNA are responsible for a “trait”. These small sections are called “Genes”. • Gene - A segment of DNA that codes for a specific trait • Trait - A characteristic an organism can pass on to it’s offspring through DNA Gene

28. Phenotype • Phenotype • Physical characteristics

29. Genotype • Phenotype • Physical characteristics • Genotype • Genes we inherit from our parents

30. Phenotype • Facial structure Notice the similarities:

31. Phenotype • Facial structure • Eyes Notice the similarities:

32. Phenotype • Facial structure • Eyes • Smile Notice the similarities:

33. Phenotype • Facial structure • Eyes • Smile • Ears Notice the similarities:

34. Phenotype • Facial structure • Eyes • Smile • Ears • Nose Notice the similarities:

35. Phenotype • Facial structure • Eyes • Smile • Ears • Nose • Neck Notice the similarities:

36. Genetics There are three basic kinds of genes: • Dominant - A gene that is always expressed and hides others • Recessive - A gene that is only expressed when a dominant gene isn’t present • Codominant - Genes that work together to produce a third trait

37. Predicting Inheritance To determine the chances of inheriting a given trait, scientists use Punnett squares and symbols to represent the genes. UPPERCASE letters are used to represent dominant genes. lowercase letters are used to represent recessive genes.

38. Predicting Inheritance For example: T = represents the gene for TALL in pea plants t = represents the gene for short in pea plants So: TT & Tt both result in a TALL plant, because T is dominant over t. t is recessive. tt will result in a short plant. Remember there are two genes for every trait! One from each parent.

39. Predicting Inheritance For example: T = represents the gene for TALL in pea plants t = represents the gene for short in pea plants So: TT & Tt both result in a TALL plant, because T is dominant over t. t is recessive. tt will result in a short plant. Remember there are two genes for every trait! Mendels’ Principle of Dominance Some genes (alleles) are dominant and others are recessive. The phenotype (trait) of a dominant gene will be seen when it is paired with a recessive gene.

40. Predicting Inheritance Let’s cross a totally dominant tall plant (TT) with a short plant (tt). Each plant will give only one of its’ two genes to the offspring or F1 generation. TT x tt T T t t

41. Predicting Inheritance Let’s cross a totally dominant tall plant (TT) with a short plant (tt). Each plant will give only one of its’ two genes to the offspring or F1 generation. TT x tt Mendels’ “Law” of Segregation Each gene (allele) separates from the other so that the offspring get only one gene from each parent for a given trait. T T t t

42. Punnett Squares The genes from one parent go here. The genes from the other parent go here.

43. Punnett Squares

44. Punnett Squares

45. Punnett Squares

46. Punnett Squares

47. Punnett Squares

48. Punnett Squares F1 generation

49. Interpreting the Results The genotype for all the offspring is Tt. The genotype ratio is: Tt - 4/4 The phenotype for all the offspring is tall. The phenotype ratio is: tall - 4/4

50. So Let’s Apply What We Know