LECTURE NOTE WEEK 11

Learning outcomes:

1

MUTATION

7.1 Overview the 7.2 Gene 7.3 Chromosomal
Classification and mutation mutation
Types of Mutation
Base substitution Chromosomal
Define mutation aberration
Base insertion
Classification Translocation
Base deletion
Spontaneous Deletion
mutation Inversion
Induced mutation Duplication

Types of mutation Chromosomal
number alteration
Gene mutation
Chromosomal Aneuploidy
mutation Euploidy/ Polyploidy

7.1 Overview the Classification
and Types of Mutation

CHAPTER 7.0: MUTATION 77..11:: MOvuetarvtiioenwCthlaesCsilfaicsastifioicnataionndaTnydpeTsypes of Mutation

WHAT IS
MUTATION?

Permanent changes in the amount, arrangement or
structure of the DNA in an organism.

 May lead to change in genotype and/ or phenotype
 Can be inherited/ can be passed to the next generation if it

occurs in gamete cells (occur during meiosis)
 Creates genetic diversity (variation) among individuals
 Mutant is the organisms that have undergone mutation.

LEARNING OUTCOMES: Define mutation

CHAPTER 7.0: MUTATION 77..11:: MOvuetarvtiioenwCthlaesCsilfaicsastifioicnataionndaTnydpeTsypes of Mutation

Classification of mutation

Spontaneous mutation Induced mutation
 Mutation caused by
 Mistakes that happen
spontaneously during DNA mutagens
replication, DNA repair, or
DNA recombination  E.g.: exposure to
mutagen
E.g.: non-disjunction during
meiosis

LEARNING OUTCOMES: Classification of mutation.

CHAPTER 7.0: MUTATION 7.1: Overview the Classification and Types of Mutation

Mutagen (mutation agent)

• Physical and chemical agents that induces changes
in DNA

Physical agent:
Ultraviolet ray
Ionizing radiation (X-ray, gamma ray, alpha
particles, neutron and electron)

Chemical agent:
Mustard gas, nitrous acid, base analogue etc.
Colchicine , ethidium bromide

LEARNING OUTCOMES: Classification of mutation.

CHAPTER 7.0: MUTATION 7.1: Overview the Classification and Types of Mutation

“tree man” Proteus syndrome: skin
gnarled warts all over overgrowth and atypical

body bone development,
Accompanied by tumors

over the body

Hyperttrichosis: An Progeria:
abnormal amount of hair resembling aspects of aging
manifested at a very early
growth over the body
age

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CHAPTER 7.0: MUTATION 7.1: Overview the Classification and Types of Mutation

Types of Mutation

Gene/ point Chromosomal
Mutation Mutation

Base substitution Chromosome Alterations of
Base insertions Aberration chromosome
Base deletions
Translocation number
LEARNING OUTCOMES: Types of mutation.
Deletion Aneuploidy
Inversion
Duplication Euploidy /
Polyploidy

7.2: Gene mutation

LEARNING OUTCOMES

• Define gene mutation.
• State the three types of gene mutation
• State the effect of base substitution (missense, nonsense, and silent mutation)

and base insertion and base deletion (frameshift mutation).

GENE MUTATION

Definition:
Changes in a single
nucleotide pair of a

gene (DNA).

(Campbell 12th Edition)

TYPES OF GENE MUTATION

1)BASE SUBSTITUTION
2) BASE INSERTION
3) BASE DELETION

12

BASE SUBSTITUTION

One or a few base pairs in
the nucleotide sequences
in genes is replaced with
another base pair.

May cause changes in a
base sequence and
results in changes in
codon .

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1) BASE SUBSTITUTION

Example :

Normal gene Mutated gene

AT AT
GC GC
CG CG
TA GC
TA TA
AT AT

T is substituted with G

EFFECT OF BASE SUBSTITUTION
Changes in codon:

Missense mutation Silent mutation Nonsense mutation

 Leads to type of amino  Changes a
amino acid codon to stop
changes acid does not codon (UAG /
change UAA / UGA )
The altered codon  no change in
protein  Most leads to a
codes for a produced non-functional
different amino protein
acid
Leads to a less- 15

active protein.

BASE SUBSTITUTION
EXAMPLE : SICKLE-CELL ANAEMIA

Erythrocyte with normal 16
hemoglobin
Erythrocyte with S
hemoglobin

E.g : Sickle Cell Anaemia
(defective in erythrocyte)

base / nucleotide T of DNA is replaced with base /
nucleotide A

missense mutation; glutamic acid is replaced with amino
acid valine (in both -chains)

have S hemoglobin (HbS) in erythrocyte
erythrocyte with HbS are sickle-shaped; inefficient oxygen
carrier

normal sickle cell
erythrocytes erythrocytes

SYMPTOMS OF SICKLE CELL ANAEMIA

 Patient suffer from anemia ~ Hb-S stiff & tend to accumulate
in small capillary.

 Can cause blockage in blood vessels.
 Hb is not efficient of transporting oxygen
 Fatal form of anemia
 Organ damages due insufficient supply of O2
 Physical weakness/ fatigue/ pale face

2) BASE INSERTION

addition of one or a few base pairs in the nucleotide
sequences in a gene

Normal gene Mutation ~base insertion

AT AT
GC GC
CG CG
TA GC
TA TA
AT TA
AT

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3) BASE DELETION

• loss of one or a few base pairs in
nucleotide sequences of a gene

Normal gene Mutated gene

AT AT
GC GC
CG CG
TA TA
TA AT
AT
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BASE INSERTION AND BASE DELETION AS A
FRAMESHIFT MUTATION

 Frameshift mutation : a mutation occurring when nucleotides
are inserted or deleted from a gene

 And the number inserted or deleted is not in a multiple of three
 Results in improper grouping of the subsequent nucleotides into codons

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BASE INSERTION AND BASE DELETION AS A FRAMESHIFT MUTATION

Base insertion @ Gene will read in Change (SHIFT) the
Base deletion the wrong three frame of triplet
base groups starting
codon on the mRNA
the points of
mutation

Results in an entirely Change in amino Change in codon
different sequence acid sequence
of amino acid from
during translation
the point of
insertion/ deletion

Different Lead to non- Harmful (e11.g. Major
polypeptide is functional protein Thalassaemia (base

produced deletion)