MUTATIONS!

1. MUTATIONS! Scott Hatfield Bullard Science Department Part One

2. MUTATIONS, PART 1:WHAT ARE THEY ?

3. MUTATIONS: • are changes in the genetic material of the cell.

4. MUTATIONS: • are changes in the genetic material of the cell. • can occur at the level of an individual DNA strand (a point mutation) or to an entire chromosome (a chromosomal mutation)

5. MUTATIONS: • usually lead to a decrease, rather than an increase, of information. • A loss of information in the cell leads to a loss of some function.

6. Information is lost….

7. Information is lost….

8. Informationis lost….

9. Information is lost….

11. The loss of information means that most mutations are either harmful or have no effect.

12. The loss of information means that most mutations are either harmful or have no effect.

13. The loss of information means that most mutations are either harmful or have no effect.

14. The loss of information means that most mutations are either harmful or have no effect.

15. . Now and then a mutation will offer a benefit to an organism.

16. . However, the idea that a single mutation would lead to a huge, dramatic change in a single generation (like the X-Men characters) is just wrong.

17. TYPES OF MUTATIONS: • Point mutations are caused by random errors in the copying process (during transcription)

18. TYPES OF MUTATIONS: • Chromosomal mutations occur when chromosomes fail to properly separate during meiosis

19. ChromosomalMutations: chromosome nucleosome DNA double helix coils supercoils histones

20. ChromosomalMutations: • changes in the number • or structure of chromosomes

21. ChromosomalMutations: • changes in the number • or structure of chromosomes • typically harmful in humans

22. ChromosomalMutations: • can occur in four different ways: • deletion, duplication, inversion and translocation

23. ChromosomalMutations: DELETION

24. ChromosomalMutations: DELETION DUPLICATION

25. ChromosomalMutations: DELETION DUPLICATION INVERSION

26. ChromosomalMutations: DELETION DUPLICATION INVERSION TRANSLOCATION

27. Non-Disjunction: • is the failure of the chromosomes • to properly separate during • meiosis Meiosis II: Meiosis I: non-disjunction homologous chromosomes fail to separate

28. Non-Disjunction: • leads to organisms with the • wrong number of chromosomes • causes birth defects like Down’s • Syndrome (trisomy-21)

29. POINTMutations: chromosome nucleosome DNA double helix coils supercoils histones

30. POINTMutations: • are changes in single base pairs of DNA • can lead to production of faulty • (misshapen) proteins, or no • protein at all

31. POINTMutations: • often have no • effect:UCC • codes for • serine, for • example, but so • does UCU, UCA • or UCG • that change the last letter in a DNA • triplet may lead to the same amino acid

32. POINTMutations: • that do this are called sense or • silent mutations

33. POINTMutations: • which lead to • a different • amino acid, • however, are • called missense • mutations • Depending on the amino acid, • these can be good, bad or neutral

34. POINTMutations: • which lead to • a stopcodon • (UAA, UAG or • UGA) are called • nonsense • mutations • These lead to loss of function • and are usually bad

35. POINTMutations: • Sense, missense and nonsense • mutations are typically caused • by substitution of one nucleotide • for another, changing the • meaning of only one codon. • Deletion or insertion of an entire • nucleotide leads to frameshift !

36. Frameshift Mutationsalter everything that follows: THE DOG ATE THE RAT MAN THE HOG ATE THE RAT MAN THE DOG ATE HER ATM AN… THE OGA TEH ERA TMA N…

38. MUTATIONS! Scott Hatfield Bullard Science Department Part Two

39. MUTATIONS, PART 2:Where Do They Happen ? ? ? ? ?

40. MUTATIONS: • can occur in any cell • that occur in gametes (eggs or sperm) are called germ-line mutations since they occur during the germination of new offspring (reproduction). • that occur in cells other than gametes are called somatic mutations

41. Somatic Mutations: Many are harmless: freckles, for example, are often the result of such mutations. (Three flies are shown above. Two are mutants. Would these be harmless mutations, or not?)

42. Somatic Mutations: Some are dangerous, because the loss of information leads to the loss of some critical function. This fruit fly was born without functional eyes, but it has a white ‘eye spot’ clearly visible on its abdomen. Flying blindly is not a favored trait !

43. Somatic Mutations: Some are dangerous, because the loss of information leads to the loss of some criticalfunction. This fruit fly was born without functional eyes, but it has a white ‘eye spot’ clearly visible on its abdomen. Flying blindly is not a favored trait !

44. Somatic Mutations: Some are dangerous, because the loss of information leads to the loss of some critical function.

45. Somatic Mutations: Some are very dangerous, because their loss triggers runaway cell division, also known as . . .

46. Cancer!

47. How does this happen? This is a picture of skin cancer on a person’s cheek, a somatic mutation, probably triggered by UV radiation

48. Substances which tend to cause mutations are called mutagens. . . High frequencies of ultraviolet light, for example, can cause point mutations which lead to skin cancer. Let’s see how this can happen . . .

49. Ultraviolet Light and Mutation Sunlight contains many frequenciesof radiation, but most are filtered out by the atmosphere.

50. Ultraviolet Light and Mutation Sunlight contains many frequencies of radiation, but most are filtered out by the atmosphere. UV-B radiationdoes get through, however, triggering a chemical change in DNA, apoint mutation