This document discusses mutations, which are changes in DNA that affect genetic information. It defines mutations as changes in the nucleotide sequence of DNA that can occur in somatic or germ cells. Most mutations are neutral, but some can be beneficial or harmful. Mutations can be inherited from parents or acquired through environmental damage or DNA copying mistakes. Different types of mutations are described, including point mutations like substitutions, insertions, and deletions, as well as frameshift, chromosome, and gene mutations. Examples of genetic disorders caused by mutations, like sickle cell anemia, phenylketonuria, albinism, and cystic fibrosis are provided. Mutagens that can increase the mutation rate such as chemicals, radiation, and ultraviolet

1. MUTATIONS
Changes in DNA that affect
genetic information

2. 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. What Causes Mutations?
 There are two ways in which DNA can
become mutated:
Mutations can be inherited.
 Parent to child
Mutations can be acquired.
 Environmental damage
 Mistakes when DNA is copied

5. 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)
Immunity to HIV

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. 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.

9. DNA (antisense strand)
mRNA
Polypeptide
Normal gene
GGTCTCCTCACGCCA
↓
CCAGAGGAGUGCGGU
Codons
↓
Pro-Glu-Glu-Cys-Gly
Amino acids
The antisense strand is the DNA strand which acts as
the template for mRNA transcription

10. Types of Gene Mutations
 Include:
Point Mutations
Substitutions
Insertions
Deletions
Frameshift

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

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

13. 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

14. No change (SILENT MUTATION)
Normal gene
GGTCTCCTCACGCCA
↓
CCAGAGGAGUGCGGU
Codons
↓
Pro-Glu-Glu-Cys-Gly
Amino acids
Substitution mutation
GGTCTTCTCACGCCA
↓
CCAGAAGAGUGCGGU
↓
Pro-Glu-Glu-Cys-Gly

15. 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

16. Frameshift Mutation
 Original:
 The fat cat ate the wee rat.
 Frame Shift (“a” added):
 The fat caa tat eth ewe era t.

17. 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

18. 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

19. Gene Mutation
Animation

20. Background to Phenylketonuria
Phenylalanine and tyrosine
are two amino acids that
humans obtain from protein
in their diet. During normal
metabolism, excess
phenylalanine is acted upon
by an enzyme
(phenylalanine hydroxide).
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21. Phenylketonuria: aka - PKU
 PKU is a hereditary
disorder caused by a
genetic defect which
disrupts this metabolic
pathway.
 An affected person lacks
the normal allele of the
gene required to make the
enzyme Phenylalanine
Hydroxide
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22. Phenylketonuria: Continued
 Owing to this inborn error in
metabolism, phenylalanine is
no longer converted to
tyrosine.
 Instead it undergoes
alternative pathways which
produces toxins which affect
the metabolism of brain cells
and severely limit mental
development.
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23. Screening for PKU –
 Newborn babies are
screened for PKU, and
sufferers are put on a diet
containing minimum
phenylalanine.
 As a result the worst
effects of PKU can be kept
to a minimum.
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24. Albinism
 Albinism results from a mutation
which prevents the formation of
enzyme 3 (Melanocyte Tyrosinase).
 As a result albinos fail to synthesize
melanin.
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25. Albinism – the symptoms
 Due to the total lack of the pigment melanin Albino’s
have characteristic
Very pale skin which fails to tan.
White hair
The colour of the iris is usually blue/gray or light
brown with some people having a reddish or violet
hue reflected through the iris.
In some cases there is vision problems.
 They must avoid ultraviolet radiation and may require to
ware tinted glasses to assist with photophobia.
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26. Albinism
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27. Cystic Fibrosis
 Mucus is a slimy substance
secreted by the inner lining of
the wind pipe and intestine.
 Mucus is made of a glycoprotein
which makes it thick, slimy and
perfect for protection and
lubrication.
 The genetic information for
coding this glycoprotein is on
chromosome 7.
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28. Cystic fibrosis:
due to gene mutation
 If the info on the gene for the glycoprotein
is altered.... Two outcomes.....
1. Homozygous for the mutant allele: Make
abnormally thick and sticky mucous leading
to lung congestion and blockage of the
pancreatic duct = CYSTIC FIBROSIS.
2. Heterozygous for the mutant allele: they carry
the mutant allele masked in their genotype
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29. Cystic fibrosis
12/11/2022 29

30. Mutagenic agents –
Increases mutation rate.
 These include
 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.
 Exposure to high-energy radiation (bombardment by
alpha, beta, or gamma particles) or ultraviolet light can
have a similar effect.
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31. Example of chemical mutations
Mrs Smith: Ch13: Mutations an
Chromosomal Abnormalities 31

32. The Chernobyl Babies –
Radiation causes birth defects
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