1. DNA Mutations

2. What Are Mutations? Changes in the nucleotide sequence of DNA

3.  May occur in somatic cells & aren’t passed to offspring  May occur in gametes (eggs & sperm) and be passed to offspring

4.  Mutations happen regularly (its very common)  Almost all mutations are neutral (doesn’t harm organism)

6.  Chemicals & UV radiation cause mutations – skin cancer

8.  Many mutations are repaired by enzymes

9.  Some type of skin cancers and leukemia result from somatic mutations  Can you “catch” cancer from someone? NO!

10.  Some mutations may improve an organism’s survival (beneficial)

11. Types of Mutations 1. Chromosomal 2. Gene

12. Chromosomal Mutations  May Involve:  Changing the structure of a chromosome  The loss or gain of part of a chromosome

13. Chromosomal Mutations  Five types exist:  Deletion  Inversion  Duplication  Translocation  Nondisjunction

14. Deletion  Due to breakage  A piece of a chromosome is lost

16. Inversion  Chromosome segment breaks off  Segment flips around backwards and reattaches

18. Duplication  Occurs when a gene sequence is repeated

20. Translocation  Involves two chromosomes that aren’t homologous (similar)  Part of one chromosome is transferred to another chromosomes

22. Nondisjunction  Failure of chromosomes to separate during meiosis (making of sperm or egg)  Causes gamete to have too many or too few chromosomes

24. Chromosome Mutation Animation

25. Disorders caused by nondisjunction: Down Syndrome Turner Syndrome Klinefelter’s Syndrome

26. Normal Female Karyotype 2n = 46

27. Normal Male Karyotype 2n = 46

28. Female Down’s Syndrome 2n = 47

29. Male, Trisomy 21 (Down’s) 2n = 47

32. Turner’s Syndrome 2n = 45

33. Klinefelter’s Syndrome 2n = 47

35. Gene Mutations  Change in the nucleotide sequence of a gene  May only involve a single nucleotide  May be due to copying errors, chemicals, viruses, etc.

36. Types of Gene Mutations  Include:  Point Mutations  Substitutions  Insertions  Deletions  Frameshift Mutations

37. Point Mutation Change of a single nucleotide Includes the deletion, insertion, or substitution of ONE nucleotide in a gene

38. Point Mutation  Sickle Cell disease is the result of one nucleotide substitution  Occurs in the hemoglobin gene

39. Deletion

41. Substitution  a single nucleotide is substituted with (or exchanged for) a different nucleotide that may result in an altered sequence of amino acidnucleotide amino acid

43. Insertion  Nucleotides are inserted into sequence altering codon pattern

46. Frameshift Mutation Inserting or deleting one or more nucleotides Changes the “reading frame” like changing a sentence Proteins built incorrectly

47. Frameshift Mutation  Original:  The fat cat ate the wee rat.  Frame Shift (“a” added):  The fat caa tet hew eer at.

49. Gene Mutation Animation