1. Mutations

2. 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
What Are Mutations?

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
Are Mutations Helpful or Harmful?

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)
Are Mutations Helpful or Harmful?

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
Chromosome Mutations

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

9. 1. Deletion Due to breakage A piece of a chromosome is lost
A B C D E F G H
A B C G H
1. Deletion

10. 2. Inversion Chromosome segment breaks off
A B C D E F G H
Chromosome segment breaks off
Segment flips around backwards
Segment reattaches
A B C F E D G H
2. Inversion

11. 3. Translocation Involves two chromosomes that aren’t homologous
A B C D E F G H
I J K L M N O P
A B C D E F G H I J
Involves two chromosomes that aren’t homologous
Part of one chromosome is transferred to another chromosome
K L M N O P
3. Translocation

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
4. Nondisjunction

15. 5. Duplication Occurs when a gene sequence is repeated A B C D E F G H
A B C D C D E F G H
Occurs when a gene sequence is repeated
5. Duplication

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.
Gene Mutations

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

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

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

22. 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?
Point Mutation (substitution)

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

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
Frameshift Mutation

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

26. Amino Acid Sequence Changed

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

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.
Does it still make sense?

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 3rd generation child Y marries a normal male, what is the probability that they will have 2 child carriers?