M U T A T I O N

Sub-Topics

Mutation classification and types

Gene mutation

Chromosomal mutation

7.1

7.2

7.3

7.1Mutation

Classification and Types

Learning Outcomes

• Define mutation (C1)

• Classify mutation to (C1)

– Gene/point mutation

– Chromosomal mutation

• State two types of mutation (C1)– Spontaneous mutation

– Induced mutation

• Define mutagen (C1)

• State types of mutagen (C1)– Physical

– chemical

Mutation classification and types7.1

What is

mutation

?

• A sudden random change in

genetic material of a cell that

potentially can cause differ in

appearance or behavior from

normal type.

What is mutation?

● This alteration can be pass from mother

to daughter cell during cell division.

● If mutation occur in reproductive cell,

it may be passed from parent to

offspring.

Classification of mutation

Types of mutation

SPONTANEOUS MUTATION

INDUCED MUTATION

A mutation occurring in

the absence of mutagens,

usually due to errors in the

normal functioning of cellular

enzymes.

e.g. non-disjunction

A mutation caused by

exposure to mutagens.

What is

mutagen?

Mutagen?● An agent that

cause an increase

in number of

mutants in a population.

● A mutagen is anything

that changes the genetic

material of an organism.

Types of

mutagen

•PHYSICAL MUTAGEN•UV rays

•Gamma rays•X-rays

•CHEMICAL MUTAGEN•Colchicine

•Ethidium bromide

7.2Gene Mutation

Learning Outcomes

• Define gene mutation (C1)

• State the four types of gene mutation (C1)

• Explain four types of gene mutation (C2)

- Base substitution

- Base insertion

- Base deletion

- Base inversion

Gene mutation7.2

Learning Outcomes

• Explain base substitution (e.g. sickle cell anaemia as missense mutation) (C2)

• State the effect of base substitution (missense, nonsense and silent mutation) and base insertion and base deletion (frameshift mutation) (C1)

• Explain base insertion and base deletion as a frameshift mutation (C2)

Gene mutation7.2

Gene Mutation

• Caused by change in nucleotide sequence of DNA within a gene.

Thymine

Cytosine

Gene Mutation

RESULT => change in amino acid sequence of polypeptide and thus different type of protein produced with abnormal function

Types of gene mutation

Base substitution may lead to missense mutation.It can cause disease such as sickle cell anaemia

Effect of base substitution

Base insertion and base deletion can

cause FRAMESHIFT mutation

What is frameshift mutation?

A type of gene mutationwhere in the addition (insertion) or deletion

of (a number of) nucleotide(s)causes a shift in the reading frame of the codons

in the mRNA,thus, may eventually lead to the alteration

in the amino acid sequence at protein translation.

M U T A T I O N

7.3Chromosomal

Mutation

Learning Outcomes

• Define chromosomal mutation (C1)

• State two types of chromosomal mutation (C1)

– Changes in chromosomal structure

– Changes in chromosomal number

• Explain changes in chromosomal structure / chromosomal aberration (C2)

• Explain types of chromosomal aberration (C2)- Translocation- Deletion (segmental

deletion) (eg. cri du chat)- Inversion- Duplication

Chromosomal mutation7.3

Learning Outcomes

• Explain alteration of chromosome number (C2)

• State the types of the alteration (C1)– Aneuploidy– Euploidy / polyploidy

• Explain aneuploidy (C2)• State aneuploidy effect on

autosomal chromosome (Monosomy 21 and Trisomy21) and sex chromosome (Klinefelter and Turnersyndrome) (C1)

• Explain autosomal abnormalities and their effects: (C2)

⮚ Monosomy (monosomy 21)

⮚ Trisomy (Down syndrome / trisomy 21)

• Explain sex chromosomalabnormalities: (C2)

⮚ Klinefelter syndrome (47, XXY)

⮚ Turner syndrome (45, XO)

• Explain euploidy/polyploidy: (C2)

⮚ Autopolyploidy

⮚ Allopolyploidy

Chromosomal mutation7.3

Chromosomal mutation?

• is any change or error that occurs within thechromosome.

• occur and change the entirety of the chromosomeitself.

Classification of Chromosomal Mutation

chromosomal

mutations

polyploidy

(euploidy)

aneuploidy

change in

structure(chromosomal aberration)

change in DNA

involving

more than one locus

change in

number

allopolyploid

y

autopolyploi

dy

translocati

on

duplication

deletion

inversion

Any changes in the normal structure of

chromosomes; often results in physical or

mental abnormalities

Types of chromosomal aberration:

- Translocation

- Deletion (segmental

deletion)

- Inversion

- Duplication

Chromosomal aberration

Types of Chromosomal aberration

Alteration of chromosome number

▪ Due to the changes in the number of chromosomes

▪ Results of errors/non-disjunction occurringduring meiosis

▪ Also may occur during mitosis

▪ May involved loss or gain of single chromosomes🡪 aneuploidy (2n+1 or 2n-1)

▪ Or increased in entire haploid sets of chromosomes🡪 euploidy (3n, 4n, 5n…)

Normal Karyotype

Effect of aneuploidy on autosomal chromosome

Monosomy 21

Effect of aneuploidy on autosomal chromosome

Trisomy 21 / Down syndrome

Effect of aneuploidy on sex chromosome

Klinefelter syndrome

Effect of aneuploidy on sex chromosome

Turner syndrome

Condition when a cell or an organism has extra one or more than one complete set of chromosomes.

Euploidy/polyploidy

2n

3n

= 6 chromosomes

= 12 chromosomes

Autopolyploidy

Allopolyploidy

Autopolyploidy vs Allopolyploidy

Autopolyploidy Allopolyploidy

Autopolyploidy occurs when an individual has more than two sets of chromosomes, both of which derived from the same parental species

Allopolyploidy occurs when an individual has more than two sets of chromosome which derived from different species