1. Mutations

2. What Are Mutations? Changes in the nucleotide sequence of DNA May occur in somatic cells (aren’t passed to offspring, only to descendant cells) May occur in germ-line cells (eggs & sperm) and be passed to offspring

3. Are Mutations Helpful or Harmful? Mutations happen regularly Almost all mutations are neutral Chemicals & UV radiation cause mutations Many mutations are repaired by enzymes

4. Types of Mutations

5. Point Mutations Change in the nucleotide sequence of a one or a few base pairs May be due to copying errors, chemicals, viruses, etc.

6. Types of Point Mutations Include: –Substitutions –Frame-shift Mutations (Insertion, Deletion)

7. Substitution One or more nucleotides are changed to a different base. AAC GCC AGC AAG GCC AGC Can cause an amino acid to be changed…or not!

8. Frame-shift Mutation Inserting or deleting one or more nucleotides Changes the “reading frame” like changing a sentence Proteins built incorrectly

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

10. Amino Acid Sequence Changed

11. Gene Mutation Animation

12. How Would the Phenotype Change?

13. Missense Substitution Sickle Cell disease is the result of one nucleotide substitution Occurs in the hemoglobin gene

14. Nonsense Substitution Thallasemia is the result of a stop codon substitution that shortens the gene Occurs in the hemoglobin gene

15. Silent Mutation The Genetic Code is repetitive – there are 64 codons that code for 20 amino acids. A silent mutation makes no change in amino acid sequence:

16. Deletion Cystic fibrosis (mucus in the lungs) is the result of one nucleotide deletion Causes a frame- shift!

17. Insertion Huntington’s Disease (nerve cell deterioration) is the result of many nucleotide insertions (CAG repeats)

18. Chromosome Mutations May Involve: –Changing the structure of a chromosome –The loss or gain of part of a chromosome

19. Chromosome Mutations Five types exist: –Deletion/Insertion –Duplication –Inversion –Translocation –Nondisjunction

20. Deletion Due to breakage A piece of a chromosome is lost Insertion An additional piece of chromosome is added

21. Deletion Cri-du-Chat is caused by a deletion in one of the chromosomes. Causes an abnormal larynx

22. Duplication Occurs when a gene sequence is repeated

23. Inversion Chromosome segment breaks off Segment flips around backwards Segment reattaches

24. Translocation Involves two chromosomes that aren’t homologous Part of one chromosome is transferred to another chromosomes

25. Translocation

26. Nondisjunction Failure of chromosomes to separate during meiosis Causes gamete to have too many or too few chromosomes Disorders: –Down Syndrome – three 21 st chromosomes –Turner Syndrome – single X chromosome –Klinefelter’s Syndrome – XXY chromosomes

28. Chromosome Mutation Animation

30. Normal Male 30

31. Normal Female 31

32. Male, Trisomy 21 (Down’s) 32 2n = 47

33. Female Down’s Syndrome 33 2n = 47

34. Turner’s Syndrome 34 2n = 45

35. Turner’s Syndrome 35

36. Klinefelter’s Syndrome 36

37. Klinefelter’s Syndrome 37