1. Chapter
12-4
DNA
Mutations

2. What Are Mutations? Changes in the nucleotide sequence of DNA
May occur in somatic cells (body cells) aren’t passed to offspring
May occur in gametes (eggs & sperm) and can be passed to offspring

3. Mutations Helpful or Harmful?
Mutations happen regularly
Almost all mutations are neutral (no effect)
Some can be harmful
Some can even be helpful!
Many mutations are repaired by enzymes

4. What causes mutations?
Chemicals, UV radiation and viruses can cause mutations
Some types of skin cancers and leukemia result from somatic mutations (harmful).
Some mutations cause genetic variation which may improve an organism’s survival (beneficial)

5. 1. Gene mutations- affects 1 gene only
Types of Mutations
1. Gene mutations- affects 1 gene only
2. Chromosomal mutations- affects parts of or whole chromosomes (many genes)

6. Gene Mutations Change in the nucleotide sequence of a gene
May only involve a change in one nucleotide
May be due to copying errors, chemicals, viruses, etc.

7. Types of GENE mutations
Point mutation (3 types) change at ONE point on DNA.
Substitution
Insertion
Deletion

8. Point Mutation Substitution in a sentence:
The fat cat ate the wee rat
substitute the “e” in ate to “t”
The fat cat att the wee rat
Doesn’t seem to change it much, but…
Sickle Cell disease and Tay Sachs disorder are both the result of one nucleotide base substitution.

9. Frameshift Point Mutation
Insertion in a sentence:
The fat cat ate the wee rat.
(insert “a” before the “t” in cat):
The fat caa tat eth ewe era t
This causes a ___________from the point of insertion.
frameshift

10. Examples of Gene Point Mutations
Substitution (changes only 1 codon – this may or may not change the protein)
DNA=AGA mRNA=_____ codes for the amino acid (aa) ________
EX. Substitute the 3rd base with “C” So DNA =_____ and mRNA  ________ (aa=________)
Now Substitute the 1st base with a “C”, So DNA=_____
And mRNA  GCU (aa=________)
Serine
ucu
AGC
Serine
UCG
CGA
Alanine

11. - DNA = CTG AAG TCT TAG CTG
2. Insertion Addition of one extra nitrogen base in the DNA or mRNA strand
- DNA = CTG AAG TCT TAG CTG
mRNA= GAC UUC AGA AUC GAC
What are the AA’s
___________ ___________ ___________
____________ _____________
(insert a “T” after 5th base in DNA)
How did it change mRNA?
______ ______ ______ ______ ______ _____
New AA’S ________ ___________ __________ __________ _________
Aspartic acid
Arginine
Phenylalanine
Isoleucine
Aspartic acid C
GAC
UUA
CAG
AAU
CGA
Aspartic
acid
leucine
Glutamine
Asparagine
Arginine

12. 3. Deletion elimination of a nitrogen base on the DNA or mRNA strand
-DNA = TGC GGC ATG ACT
mRNA= ACG CCG UAC UGA
What are the AA’s
________ _________ __________ __________
(Delete the 2nd base in DNA)
How did it change mRNA?
______ ______ ______ ______
New AA’S ________ ___________ __________
Threonine
Proline
Tyrosine
Stop
AGC
CGU
ACU GA
Serine
Arginine
Threonine

13. Frameshift- causes a shift in all codons after the point mutation.
Which of the three point mutations could cause a frameshift?
_________________
INSERTION
DELETION

14. Amino Acid Sequence Changed
How would this change
Amino acid sequence?

15. Gene Mutation Animation
Click Here for Nova- ‘One Wrong Letter’

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

18. Types:
Deletion
Inversion
Translocation
Nondisjunction
Duplication

19. Deletion
Due to breakage
A piece of a chromosome is lost

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

21. Duplication
Occurs when a gene sequence is repeated

22. Translocation
Involves two chromosomes that aren’t homologous (pair of chromosomes that code for the same traits)
Part of one chromosome is transferred to another chromosome

23. Translocation

24. Nondisjunction Failure of chromosomes to separate during meiosis
Causes gamete to have too many or too few chromosomes

25. Trisomy-three chromosomes instead of two
Monosomy-one chromosome
instead of two

26. Chromosome Mutation Animation