Biochem mutations

1. MutationsMutations

2. What Are Mutations?What Are Mutations?
•Changes 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. Types of Mutations

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

7. Chromosome Mutations
•Five types exist:
–Deletion
–Inversion
–Translocation
–Nondisjunction
–Duplication

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

9. Inversion
•Chromosome segment breaks off
•Segment flips around backwards
•Segment reattaches

10. Duplication
•Occurs when a gene sequence is repeated

11. Translocation
•Involves two chromosomes that aren’t
homologous
•Part of one chromosome is transferred to
another chromosomes

12. Translocation

13. Nondisjunction
•Failure of chromosomes to separate
during meiosis
•Causes gamete to have too many or too
few chromosomes
•Disorders:
–Down Syndrome – three 21
st
chromosomes
–Turner Syndrome – single X chromosome
–Klinefelter’s Syndrome – XXY chromosomes

15. Chromosome Mutation
Animation

17. 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.

18. Types of Gene Mutations
•Include:
–Point Mutations
–Substitutions
–Insertions
–Deletions
–Frameshift

19. Point Mutation
•Change of a single nucleotide
•Includes the deletion, insertion, or
substitution of ONE nucleotide in a
gene

20. Point mutatioin may be transitions
or transversioins

21. Effects
1.Silent mutation
No detectable effect Especially if the changes is at the third position of the codon
eg. AAA - AAG
2. Missense effect (mistaken amino acid)
A. acceptable
B. partially acceptable
c. Unacceptable
3. Nonsense effect
Premature termination
of amino acid incoporation

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

24. Frameshift Mutation
•Inserting or deleting one or more nucleotides
•Changes the “reading frame” like changing a
sentence
•Proteins built incorrectly

25. Amino Acid Sequence
Changed

26. Gene Mutation Animation