1. Mutations

2. What Are Mutations? MUTATION = A change in the nucleotide sequence of DNA May occur in somatic cells (aren’t passed to offspring) May occur in gametes (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. Are Mutations Helpful or Harmful? Some type of skin cancers and leukemia result from somatic mutations Some mutations may improve an organism’s survival (beneficial)

5. So…Are Mutations Helpful or Harmful?

6. Types of Mutations

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

8. Chromosome Mutations Five types exist: Deletion Inversion Translocation Nondisjunction Duplication

9. 1. Deletion Due to breakage A piece of a chromosome is lost ABCDEFGHABCDEFGH ABCGHABCGH

10. 2. Inversion Chromosome segment breaks off Segment flips around backwards Segment reattaches ABCDEFGHABCDEFGH ABCFEDGHABCFEDGH

11. 3. Translocation Involves two chromosomes that aren’t homologous Part of one chromosome is transferred to another chromosome ABCDEFGHABCDEFGH ABCDEFGHIJABCDEFGHIJ IJKLMNOPIJKLMNOP KLMNOPKLMNOP

13. 4. Nondisjunction Failure of chromosomes to separate during meiosis Causes gamete to have too many or too few chromosomes Example : Down Syndrome (Trisomy 21) – caused by ___ copies of chromosome 21

15. 5. Duplication Occurs when a gene sequence is repeated ABCDEFGHABCDEFGH ABCDCDEFGHABCDCDEFGH

16. Chromosome Mutation Animation

18. 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.

19. Types of Gene Mutations Include: Point Mutations Substitutions Frameshift Insertion Deletion

20. 1. Point Mutation Change of a single nucleotide Usually includes the substitution of ONE nucleotide in a gene

21. Point Mutation Sickle Cell disease is the result of one base substitution Occurs in the hemoglobin gene

22. Point Mutation (substitution) Original: The fat cat ate the wee rat. Point Mutation (“a” subs for “t”): The fat caa ate the wee rat.

23. Point Mutation (substitution) The fat caa ate the wee rat. Is the sentence still understandable? Would a point mutation likely cause big problems? What do the simple, three- letter words above represent?

24. Frameshift Mutation Inserting or deleting one or more nucleotides Changes the “reading frame” like changing a sentence Can cause proteins to be built incorrectly

25. Frameshift Mutation Original: The fat cat ate the wee rat. Frame Shift (“a” added): The fat caa tat eth ewe era t.

26. Amino Acid Sequence Changed

27. Frameshift Mutation Cystic Fibrosis is the result of a frameshift mutation 2 frameshifts in the CFTR gene: 2-base insertion 1 base deletion

28. Gene Mutation Animation

29. Does it still make sense? If a gene mutation does not change the amino acid, it’s called a SILENT mutation. If a gene mutation changes the amino acid, it’s called a MISSENSE mutation. If a gene mutation changes the amino acid to a “stop” codon, it’s called a NONSENSE mutation.

30. End notes…

31. What is the probability of child V being affected? What is the chance that child V will be a carrier for the disease? If 3 rd generation child Y marries a normal male, what is the probability that they will have 2 child carriers?