1. MUTATIONS

2. WHAT ARE MUTATIONS?
KEY CONCEPT: Mutations are changes in genetic material. VOCABULARY: Mutation, point mutation, frameshift mutation, polyploidy

3. What happens when a protein malfunctions?
If a protein can't do its job, then cells containing that protein may not function properly.
Since humans are composed of cells, a malfunction may lead to medical problems.

4. HOW DO MUTATIONS HAPPEN?
There are two ways in which DNA can become mutated:
1. Mutations can be inherited. This means that if a parent has a mutation in his or her DNA, then the mutation is passed on to his or her children.
2. Mutations can be acquired. This happens when environmental agents damage DNA, or when mistakes occur when a cell copies its DNA prior to cell division.

5. Here's another way to think about it!
Think of a cell as a car. A car is made up of many parts, just as a cell is made up of many proteins.
Each part -- or protein -- does a specific job.

6. ANALOGY
What happens when a part breaks on your car?
It depends!
If one headlight burns out, you can still drive the car, although driving at night may be tough.

7. ANALOGY Proteins in cells work the same way.
Some proteins are more important to a cell's normal function than others.
A cell might still be able to function properly if the mutated protein isn't that important, like the headlight on your car.

8. ANALOGY
But when your brakes fail, you're really in trouble -- before you know it, your car is cruising out of control!
And if you're driving in traffic when this happens, then your car troubles are certain to affect the cars around you, making problems for the whole street.

9. KINDS OF MUTATIONS
MICROMUTATIONS:
Gene mutations result from changes in a single gene.

10. KINDS OF MUTATIONS
2. MACROMUTATIONS: Chromosomal mutations involve changes in whole chromosomes.

11. MICROMUTATIONS OR GENE MUTATIONS
Point Mutations
Affect one nucleotide
Occur at a single point in the gene sequence
Three Types:
Substitution
Insertion
Deletion

12. Point Mutations Substitution
A single nucleotide is changed in the nucleotide sequence.
This may result in a change to a single amino acid in the protein.
The change to a single amino acid may or may not alter the proteins function.

13. Point Mutations - Substitution
Codon =
Amino Acid
UGU
Original
Cysteine
UGC
No Change
UGG
Single AA
Tryptophan
UGA
Bad
STOP

14. GENE MUTATION: SUBSTITUTION
DNA: TAC GCA TGG ATT mRNA: AUG CGU ACC UUA Amino Acid:
MET
ARG
THR
LEU
Substitution
DNA: TAC GTA TGG ATT
mRNA: AUG CGU ACC UUA
Amino
Acid:
MET
HIS
THR
LEU

15. Substitution Mutations
Transition
3’AGTTCAG-TAC-TGA-ACA-CCA-TCA-ACT-GATCATC5’
5’AGUC-AUG-ACU-UGU-GGU-AGU-UGA-CUAGAAA3’
Met
Thr
Cys
Gly
Ser
Pyrimidine to
Pyrimidine
3’AGTTCAG-TAC-TGA-ATA-CCA-TCA-ACT-GATCATC5’
5’AGUC-AUG-ACU-UAU-GGU-AGU-UGA-CUAGAAA3’
Met
Thr
Gly
Ser
Tyr
Transversion
3’AGTTCAG-TAC-TGA-ACA-CCA-TCA-ACT-GATCATC5’
5’AGUC-AUG-ACU-UGU-GGU-AGU-UGA-CUAGAAA3’
Met
Thr
Cys
Gly
Ser
Purine to
Pyrimidine
3’AGTTCAG-TAC-TGA-AAA-CCA-TCA-ACT-GATCATC5’
5’AGUC-AUG-ACU-UUU-GGU-AGU-UGA-CUAGAAA3’
Met
Thr
Gly
Ser
Phe

16. Insertions & Deletions
Point Mutations
Frameshift Mutations
Result From
Insertions & Deletions
A nucleotide is added, or subtracted from the nucleotide sequence. This shifts the Codon grouping and drastically alters the amino acid sequence in the protein.

17. GENE MUTATION: INSERTION
DNA: TAC GCA TGG ATT mRNA: AUG CGU ACC UUA Amino Acid:
MET
ARG
THR
LEU
Insertion
DNA: TAT CGC ATG GAA T
mRNA: AUA GCG UAC CUU A
Amino
Acid:
ILE
ALA
TRY
LEU

18. GENE MUTATION: DELETION
THE
FAT
CAT
ATE
THE
RAT
Deletion
THE F
AT C
AT A
TE T
HE R AT AT
TEF
ATC
ATA
TET
HER
The loss of a single DNA base can change the entire message that DNA sends to make a protein!
DIFFERENT DNA MESSAGE = DIFFERENT PROTEIN

19. Frame Shift Mutations 3’AGTTCAG-TAC-TGA-ACA-CCA-TCA-ACT-GATCATC5’
3’AGTTCAG-TAC-TGA-AAC-CAT-CAA-CTG-ATCATC5’
3’AGTTCAG-TAC-TGA-ACA-CCA-TCA-ACT-GATCATC5’
5’AGUC-AUG-ACU-UGU-GGU-AGU-UGA-CUAGAAA3’
Met
Thr
Cys
Gly
Ser
5’AGUC-AUG-ACU-UUG-GUA-GUU-GAC-UAG-AAA3’
Met
Thr
Val
Leu
Frame shift mutations tend to have a dramatic effect on proteins as all codons down stream from the mutation are changed and thus code for different amino acids. As a result of the frame shift, the length of the polypeptide may also be changed as a stop codon will probably come at a different spot than the original stop codon.

20. MACROMUTATIONS: CHROMOSOMAL MUTATIONS
Changes the number or structure of chromosomes
As a result the locations of genes on chromosome or the number of copies of some genes may change.

21. MACROMUATIONS: CHROMOSOMAL MUTATIONS
1 Deletions - Loss of chromosome sections 2 Duplications - Duplication of chromosome sections 3 Inversions - Flipping of parts of chromosomes 4 Translocations - Movement of one part of a chromosome to another part

22. MACROMUTATION: DELETIONX
Deletion
Loss of all or part of a chromosome

23. MACROMUTATION: DELETION
Original
chromosome
Centromere
A B C D E F G H
Genes
A B C D G H
New Chromosome
E F

24. MACROMUTATION DUPLICATION
Segment of chromosome is repeated

25. MACROMUTATION: DUPLICATION
Original
chromosome
Centromere
A B C D E F G H
Genes
E F
Duplication
New Chromosome
A B C D E F E F G H

26. MACROMUTATION: INVERSION
Chromosome or part of a chromosome is placed in the reverse direction

27. MACROMUATION: INVERSION
Original
chromosome
Centromere
Genes
A B C D E F G H
Inversion
New chromosome
A B C D F E G H

28. MACROMUTATION: TRANSLOCATION
Part of one chromosome breaks off and attaches to another
chromosome

29. MACROMUTATION: TRANSLOCATION
Original
Chromosome
Centromere
Genes
A B C D E F G H
New chromosome
A B E F C D G H

30. SIGNIFICANCE OF MUTATIONS
Most mutations are NEUTRAL— they have little or no effect on genes or the function of proteins.
We all have mutations within our DNA

31. HARMFUL MUTATIONS
Mutations can cause a dramatic changes in the protein structure are often HARMFUL.
THESE DEFECTIVE PROTEINS CAN DISRUPT NORMAL BIOLOGICAL ACTIVITIES.
Harmful mutations are associated with many types of cancer.

32. BENEFICIAL MUTATIONS
Mutations are also the source of GENETIC VARIATION in a species.
Beneficial mutations may produce proteins with new or altered activities that can be useful to organisms in different or changing environments.

33. BENEFICIAL MUTATIONS
POLYPLOIDY: organism has extra sets of chromosomes
When a complete set of chromosomes fail to separate during meiosis, the gametes that result may produce
TRIPLOID (3N) or TETRAPLOID (4N)
organisms.

34. BENEFICIAL MUTATIONS
Polyploid plants are often larger and stronger than diploid plants.
Important crop plants have been produced in this way.
Example: bananas, citrus fruits, seedless plants

35. INHERITED MUTATIONS
DNA fails to copy accurately Most of the mutations that we think matter to evolution are "naturally-occurring."
For example, when a cell divides, it makes a copy of its DNA — and sometimes the copy is not quite perfect. That small difference from the original DNA sequence is a mutation.

36. INHERITED MUTATIONS

37. EXTERNAL INFLUENCES CAUSE MUTATIONS
Mutations can be caused by exposure to
specific chemicals or radiation. These agents cause the DNA to break down.

38. EXTERNAL INFLUENCES CAUSE MUTATIONS
This is not necessarily unnatural — even in the most isolated and pristine environments, DNA breaks down. Nevertheless, when the cell repairs the DNA, it might not do a perfect job of the repair. So the cell would end up with DNA slightly different than the original DNA and hence, a mutation.