Mutations are changes in the genetic material, affecting DNA sequences, with varying impacts on organisms. They can be beneficial, harmful, or neutral and only those in gametes are inherited. Types of mutations include point mutations, deletions, insertions, and chromosomal alterations, caused by errors in DNA replication or exposure to mutagens.

1. GENOME
ALTERATIONS
VPHY 241 PHYSIOLOGICAL BIOCHEMISTRY

2. MUTATION
 Mutations are changes in genetic
material; changes in the nucleotide
sequence of DNA.
 In gene mutations, the DNA code will
have a base (or more) missing, added, or
exchanged in a codon.

3. MUTATION
 It may involve large sections of
chromosomes or single base pairs
 Mutations can change the reading
frame of a gene transcript.

4. How common are mutations?
 Mutations occurs at a frequency of about
1 in every 1 billion base pairs.
 Mutations happen regularly
 Almost all mutations are neutral
 Chemicals & UV radiation cause
mutations
 Many mutations are repaired by enzymes

5. Manifestations of mutation
 Mutations are not always seen. The
affected gene may still function.
 Mutations may be harmful.
 Mutations may be beneficial.
 Mutations may have no effect on the
organism.

6. How do mutations affect the
population?
 Mutations are a major source of
genetic variation in a population
increasing biodiversity.
 Some variations may help them to
survive better.

7. How are mutations inherited?
 Only mutations in gametes are passed
onto offspring.
 Mutations in somatic cells only affect
the organism in which they occur and
are not passed onto offspring.

8. TYPES OF
MUTATIONS

9. CHROMOSOME MUTATIONS
May Involve:
 Changing the structure of a
chromosome
 The loss or gain of part of a
chromosome

10. Chromosome Mutations
Five types exist:
1. Deletion
2. Inversion
3. Translocation
4. Nondisjunction
5. Duplication

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

12. Inversion
 Chromosome segment breaks off
 Segment flips around backwards
 Segment reattaches

13. Duplication
Occurs when a gene sequence is repeated.

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

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

16. 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
 Point Mutation
 Substitution
 Insertion
 Deletion

19. POINT MUTATION
 Occurs when the base sequence of a
codon is changed.
There are 3 types:
1. Substitution
2. Deletion
3. Insertion

20. The Genetic Code is a triplet code
Peter J. Russell, iGenetics: Copyright © Pearson Education, Inc., publishing as Benjamin Cummings.

21. Substitution Mutations
 Normal DNA: CGA – TGC – ATC
Alanine – Threonine – stop
 Mutated DNA: CGA – TGC – TTC
Alanine – Threonine - Lysine
 A single nitrogen base is substituted for another in
a codon.
 It may or may not affect the amino acid or protein.

22. Mutations: Substitutions
Substitution mutation
GGTCACCTCACGCCA
↓
CCAGUGGAGUGCGGU
↓
Pro-Arg-Glu-Cys-Gly
Substitutions will only affect a single codon
Their effects may not be serious unless they affect an amino acid that is
essential for the structure and function of the finished protein molecule (e.g.
sickle cell anaemia)
Normal gene
GGTCTCCTCACGCCA
↓
CCAGAGGAGUGCGGU
Codons
↓
Pro-Glu-Glu-Cys-Gly
Amino acids
© 2010 Paul Billiet ODWS

23. No change
Normal gene
GGTCTCCTCACGCCA
↓
CCAGAGGAGUGCGGU
Codons
↓
Pro-Glu-Glu-Cys-Gly
Amino acids
Substitution mutation
GGTCTTCTCACGCCA
↓
CCAGAAGAGUGCGGU
↓
Pro-Glu-Glu-Cys-Gly

24. Disaster
Normal gene
GGTCTCCTCACGCCA
↓
CCAGAGGAGUGCGGU
Codons
↓
Pro-Glu-Glu-Cys-Gly
Amino acids
Substitution mutation
GGTCTCCTCACTCCA
↓
CCAGAAGAGUGAGGU
↓
Pro-Glu-Glu-STOP
© 2010 Paul Billiet ODWS

25. Insertion Mutations
 Normal DNA: CGA – TGC – ATC
Alanine – Threonine – stop
 Mutated DNA: CGA – TAG – CAT – C
Alanine – Leucine - Valine
 A nitrogen base is inserted/added to the sequence.
 It causes the triplet “frames” to shift.
 It always affects the amino acids and,
consequently, the protein.

26. Mutations: Additions
Normal gene
GGTCTCCTCACGCCA
↓
CCAGAGGAGUGCGGU
Codons
↓
Pro-Glu-Glu-Cys-Gly
Amino acids
Addition mutation
GGTGCTCCTCACGCCA
↓
CCACGAGGAGUGCGGU
↓
Pro-Arg-Gly-Val-Arg
A frame shift mutation
© 2010 Paul Billiet ODWS

27. Deletion Mutations
 Normal DNA: CGA – TGC – ATC
Alanine – Threonine – stop
 Mutated DNA: CGA – TCA – TC
Alanine – Serine
 A nitrogen base is deleted/removed from the
sequence.
 It causes the triplet “frames” to shift.
 It always affects the amino acids and, consequently, the
protein.

28. Mutations: Deletions
Normal gene
GGTCTCCTCACGCCA
↓
CCAGAGGAGUGCGGU
Codons
↓
Pro-Glu-Glu-Cys-Gly
Amino acids
Deletion mutation
GGTC/CCTCACGCCA
↓
CCAGGGAGUGCGGU
↓
Pro-Gly-Ser-Ala-Val
A frame shift mutation
© 2010 Paul Billiet ODWS

30. Point Mutations
 Substitution has the least effect because it
changes only one amino acid or it may
change no amino acid.
 Deletion or insertion mutations are most
disruptive because they change the reading
frame, causing a frame shift.

32. Gene Mutation
 An example of a substitution
mutation is sickle cell anemia.
 Only one amino acid changes in
the hemoglobin.
 The hemoglobin still functions
but it folds differently changing
the shape of the RBC.

33. Mutation
Normal Hemoglobin Sickle Cell Hemoglobin
DNA GGA CTT GCA GGA CAT GCA
mRNA CCU GAA CGU CCU GUA CGU
A.A. PRO GLU ARG PRO VAL ARG

34. Gene Mutation
 Huntington’s Disease is caused by
an insertion mutation.
 People with this disorder have
involuntary movement and loss of
motor control. They eventually
have memory loss and dementia.
The disease is terminal. Huntington Disease Located
on chromosome 4
First Gene Disease Mapped

35. Gene Mutation
 When does a gene mutation
have the greatest affect on an
organism?
 When it occurs in the gamete or
early in embryonic development
(in stem cells or first few days). Four cell Zygote

36. What causes Mutations?
 Errors in DNA Replication
 Errors in chromosome crossover in meiosis
 Mutagens

37. Mutagens
 Physical or chemical factors that causes the DNA code to change
(mutate);
 May increase mutation rate.
• UV Radiation and X-Rays
• Chemicals like DDT
A variety of chemicals act as mutagens. E.g.
 Bromouracil, are structurally similar to DNA bases, and are inserted in place
of normal bases.
 Ethidium bromide has a structure that allows it to wedge within the DNA
double helix
 Peroxides and mustard gas, chemically modify DNA.

38. The Chernobyl Babies – Radiation causes
birth defects
38

39. Albinism
• Albinism results from a mutation which prevents the formation of enzyme 3
(Melanocyte tyrosinase).
• As a result albinos fail to synthesize melanin.

40. Example of chemical mutations
Mrs Smith: Ch13: Mutations an
Chromosomal Abnormalities