1. MUTATIONS

2. MUTATIONS
ANY change in the DNA sequence that affects genetic information
Changes may be good or bad
There may or may not be a visible effect in an organism or its offspring…

3. So...when are mutations inherited?
Mutations will only be passed on to offspring if they occur in the gamete (sex cells)

4. When are mutations inherited?
Mutations that occur in regular body cells (somatic cells) will be lost when the cell dies
Mutation in lung cell will lead to cancer, but cancer isn’t passed on to offspring

5. When are mutations inherited?
Lethal mutations result in the death of the organism
Often miscarriage

6. What causes mutations?
No real known cause—
occur spontaneously
occur randomly

7. Mutagens may cause changes
X-rays
Ultraviolet rays
Microwaves
Cosmic radiation
Chemicals:
Benzene
Asbestos
Formaldehyde
Toxic industrial chemicals

8. Two Types 1. GENE MUTATIONS— 2. CHROMOSOMAL MUTATIONS—
changes in a single gene
2. CHROMOSOMAL MUTATIONS—
changes in whole chromosomes (chromosome number or chromosome itself)

9. 1. GENE MUTATIONS a. POINT MUTATION (Substitution)
Single nucleotide is substituted for the wrong one
Ex: A-G instead of A-T
This can lead to…

10. 1. GENE MUTATIONS
1) Silent mutation: has NO effect since some amino acids have multiple sequences
Ex: CUC codes for leucine
CUA also codes for leucine

11. 1. GENE MUTATIONS
2) Missense mutation: causes the wrong amino acid to be in sequence
Ex: CUU codes for leucine
CCU codes for proline

12. 1. GENE MUTATIONS 3) Nonsense mutation: causes an early STOP codon
Ex: UCA codes for serine
UGA codes for STOP

13. POINT MUTATION—SUBSTITUTION
THE
ATE
CAT
FAT
RAT
HAT

14. 1. GENE MUTATIONS b. FRAMESHIFT MUTATION
insertion or deletion of one or more nucleotides
All codons are shifted
May cause serious effects
Such mutations can alter a protein so that it is unable to perform its normal functions.

15. FRAMESHIFT MUTATION— DELETION
THE
ATE
CAT
FAT
RAT
TEF
TET
ATA
ATC
HER AT X

16. FRAMESHIFT MUTATION— INSERTION
THE
ATE
CAT
FAT
RAT
TAT
TCA
FLA
ETH
ERA T

17. 2. CHROMOSOMAL MUTATIONS
a. DELETION
Involves loss of a part or whole chromosome

18. F E D A B C A C
DELETION F E D

19. 2. CHROMOSOMAL MUTATIONS
b. DUPLICATION
Opposite of deletion
A segment of the chromosome is repeated

20. A B F E D A B C B F E D C
DUPLICATION

21. 2. CHROMOSOMAL MUTATIONS
c. INVERSION
Direction of genes is reversed within chromosome (part is upside-down)

22. F E D A B C A E D
INVERSION C B F

23. 2. CHROMOSOMAL MUTATIONS
d. TRANSLOCATION
When part of a chromosome breaks off and relocates to another part

24. F E D A B C L K J G H I F E D A B C L K J G H I
TRANSLOCATION

25. 2. CHROMOSOMAL MUTATIONS
e. NONDISJUNCTION
Results in too few or too many chromosomes in a cell…

26. NONDISJUNCTION MONOSOMY
Having only ONE copy of a chromosome instead of TWO
EX: Turner’s syndrome (has only one X chromosome)

27. NONDISJUNCTION TRISOMY
Having THREE copies of a chromosome instead of TWO
EX: Down Syndrome (3 copies of chromosome #21, trisomy 21)

28. NONDISJUNCTION

29. Where can mutations occur?
Somatic Cells (Body Cells)
Germ Cells (Sex Cells)

30. Somatic Cells (Body Cells)
During or before mitosis
All new cells will also be altered
The change is permanent
Only effects organism, not offspring

31. Germ Cells (Sex Cells)
Changes can occur in egg/sperm before, during or after meiosis
Altered egg/sperm may be fertilized—passing change to offspring
Changes may or may not be harmful
Harmful changes cause birth defects