13 Chapter 12 Teacher Copy

Jisrun Najaah Fi Ilmi Al Insan Chapter 12: Variation

CHAPTER 12

Variation

“Wahai umat manusia! Sesungguhnya Kami telah
menciptakan kamu dari lelaki dan perempuan, dan
Kami telah menjadikan kamu berbagai bangsa dan
bersuku puak, supaya kamu berkenal-kenalan (dan

beramah mesra antara satu dengan yang lain).
Sesungguhnya semulia-mulia kamu di sisi Allah
ialah orang yang lebih taqqanya di antara kamu,
(bukan yang lebih keturunan atau bangsanya).
Sesungguhnya Allah Maha Mengetahui, lagi Maha
Mendalam PengetahuanNya (akan keadaan dan

amalan kamu)”
Al Hujuraat ayat 13

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Jisrun Najaah Fi Ilmi Al Insan Chapter 12: Variation

12.1 TYPES AND FACTORS OF VARIATION

Definition of Variation

1. Refers to the differences in physical characteristics observed in phenotypic
Caused by changes in structure, physiology and biochemistry

2. Found within the same population or species
3. All organism is different although they are from the same species including identical twins
4. Variation enables us to identify individuals within a population.

The Necessity of Variation for the Survival of Species

1. Variation plays an important role in evolution
2. Forms the basis of natural selection.

Evolutionary force that selects beneficial genes
Removes the non-beneficial ones from the natural environment
3. Species that possess phenotypes which enable them to adapt to their surrounding will
continue to live and breed for the survival of the species
4. Species that not possess phenotypes which enable them to adapt to their surrounding will
die and extinct

Polluted environment Unpolluted environment
Black moth species will extinct
Black moth species will survive White moth species will survive
White moth species will extinct
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Brace Enables natural environment to continue
map selecting beneficial characteristics and remove
the non-suitable ones

Necessity Of Allows cross breeding among species to form
Variation new species

Ensures survival of the species when the
environment changes

Types Of Variation and Comparison between Continuous and Discontinuous Variation

Characteristic Continuous variation Discontinuous variation

1. Different Not distinctive in characteristic Distinct differences in
between Normal distribution characteristic
individual Discrete distribution

2. Graph Most members of the population There are no intermediate
distribution have intermediate phenotypes characteristics
Characteristics found in between
Qualitative measurement
the two extremes Cannot be measured or graded)

Quantitative measurement Controlled by single gene with
two or three alleles involve
3. Measurement Can be measured and graded
from one extreme to the other

extreme

4. Number of Large number of genes are

gene involved

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Jisrun Najaah Fi Ilmi Al Insan Chapter 12: Variation

Characteristic Continuous variation Discontinuous variation
Bell-shaped curve Separated bar chart

5. Graph shape

6. Factor of Characteristic is influenced by Characteristic is influenced by
influences environmental factor genetic factor

7. Inheritance Cannot be inherited Can be inherited

8. Examples Weight, height, skin colour and Tongue rolling, fingerprints,
intelligence. earlobes, blood group, eyes
colours

Similarity between Continuous and Discontinuous Variation
Both shows differences in characteristics among individuals of the same species

CAUSES OF VARIATION Tree
map

Type Type
Continuous Variation Continuous Variation
Factor
Factor

Environmental factor Genetic factor

Light Temperature pH Mutation Random Crossing Independent
fertilization over assortment

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Genetic Factors
Crossing Over 1. Crossing over occurs between non-sister chromatids
of homologous chromosomes
Prophase I
2. During prophase I of meiosis
Anaphase II 3. Recombination produces new combinations of genes

Anaphase II

4. Sister chromatids that separate during
anaphase II of meiosis

5. Form gametes with different genetic
materials at the end of meiosis

Draw possibility of chromosomes in a gamete
produces after meiosis II completed

Independent Assortment of Chromosomes
1. Homologous chromosome pair is arranged randomly on the equatorial plane of a cell

Originated from one maternal chromosome and one paternal chromosome
2. During metaphase I of meiosis
3. Different gametes will be produced
4. Different combinations of paternal and maternal chromosomes at the end of meiosis,

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Draw the combination of homologous chromosomes based of random assortment in diagram
below

Bio Quiz:
If two pairs of chromosomes produce 4 daughter cells with new combination of gene, how
many combinations of gene in human during independent assortment?
Answer = 223

= 8, 388, 608 combination of gene

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Jisrun Najaah Fi Ilmi Al Insan Chapter 12: Variation

Random fertilisation

1. Fertilisation between sperm and secondary oocyte is random
2. Gamete’s produced is having different genetic contents from their parents
3. Caused by;

Genetic recombination which occurs during crossing over
Random arrangement of homologous chromosomes in meiosis
4. Diploid zygote which is produced after fertilisation will have a new genetic combination

Ovum

Random fertilisation

Sperm 1 Sperm 2 Sperm 3 Sperm 4

Zygote 1 Zygote 2 Zygote 3 Zygote 4

Draw possibility combination of chromosome in a zygote produced after fertilization
is completed

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Mutation

1. Permanent change which occurs spontaneously on genes or chromosomes

2. Mutation creates new genotypes

3. If mutation occurs in;

Gamete - Characteristics determined by mutated genetic materials can

be inherited

- Also known as mutation of germ cell

- Such as Haemophilia and colour blind

Somatic cell - Can cause variation

- Characteristics cannot be inherited by the next generations.

Environmental Factors

1. Environmental factors that cause variation include abiosis factors such as;
Temperature
Light
pH

2. Effect of environment on variation is small
3. Only involves phenotypic differences and not genotypic differences
4. Environment can change allele frequency and genotype frequency in a population

Cannot change the genotype
5. Environmental variation cannot be inherited from one generation to the next

Light

1. Sunlight can alter skin colour
2. People who are under the sun for a long period of time will have tanned skin
3. Ultraviolet rays in sunlight can destroy melanin pigment of exposed skin
4. More melanin pigment will be produced

Cause the skin to be darker.

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Temperature Explanation
Animal
Inherited the gene which produces dark pigment enzyme for fur colour
Siamese cat This enzyme only functions at temperature less than the body
temperature
Reptile Such as the ears, face, tail and paws

Fish o These body parts are dark in colour.
In turtle, 28°C - 31°C is optimum temperature to get sex ratio from 1:1
(males: females)
Eggs hatching at temperatures below than 28°C become male
Eggs hatching at temperatures higher than 31°C become female
26°C-28°C is optimum temperature to get sex ratio from 1:1 (males:
females) in most fish
Small changes of just 1-2°C can significantly alter the sex ratio from
1:1 (males: females) up to 3:1
Eggs hatching at temperatures below than 26°C become female
Eggs hatching at temperatures higher than 28°C become male

pH

pH of Soil

Acidic Alkaline
Hydrangea sp. plant produces blue flowers Hydrangea sp. plant produces pink flowers
pH less than 5.5 pH in alkaline soil.

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Interactions between Genetic and Environmental Factors

1. Environmental factors can interact with genetic factors to cause variation
2. Environmental factors determine the phenotypes
3. Characteristics inherited from parents such as height, intelligence and skin colour are

greatly influenced by environmental factors

J and N are identical twins.
Both have similar genotype for
obesity since they originated
from the same embryo

J and N were separated since childhood.

J likes low fat diet and N likes high fat diet and does
enjoys physical activities not like physical activities.

J has an ideal body weight. N is obese

Conclusion:
Differences in eating habits and environment while growing up produce different phenotypes.

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12.2 VARIATION IN HUMANS

Relation of Variation to Human Inheritance

1. Human trait is controlled by a pair of alleles which are dominant allele or recessive allele
2. Dominant trait is observed when both dominant alleles are present or when one dominant

allele is paired with a recessive allele
3. Recessive trait is only shown when both recessive alleles are present
4. These genetic information causes variation in humans

Traits in humans

Characteristics Dominant Recessive

Height Tall Short
Type of hair
Tendency to use hands Curly hair Straight hair
Presence of dimples
Ability to roll tongue Right-handed Left-handed
Type of earlobes
Presence Absence

Can roll tongue Cannot roll tongue

Free earlobes Attached earlobes

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12.3 MUTATION

1. Spontaneous and random change of genetic material
Known as DNA of the cell in an organism

2. Mutagen is a substance which causes mutation or increases the mutation rate to a
dangerous level

3. Mutation occurs spontaneously in natural conditions
4. New genetic material produced by mutation is called a mutant
5. A mutant can exist as mutant gene, mutant cell, mutant organelle or mutant individual.

Mutagen

Brace Virus
map
Bacteria
Biological Carcinogen in cigarette smoke
agent Food preservatives

Types Of Chemical
Mutagens agents

Benzene

Formaldehyde
Ultraviolet from the sun

Physical X- Ray
agents Alpha ray

Ionising
rays

Beta ray
Gamma ray

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Types of Mutations

Gene Mutation

1. Occurs when there is a change in nucleotide base Original nucleotide sequence
sequence of a gene Mutation point
Also known as point mutation

2. Change alters the genetic code that is used to
synthesise amino acidProtein structure will be change
and this new protein cannot function

3. Gene mutation occurs by;
Base substitution
Base deletion
Base insertion

4. Gene mutation causes genetic diseases such as
thalassemia, cystic fibrosis, sickle cell anaemia,
albinisme and haemophilia

Nucleotide sequence after mutation

List of Amino Acid

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Jisrun Najaah Fi Ilmi Al Insan Chapter 12: Variation

Complete the DNA sequence below based on the list of amino acid given

Base substitution Base insertion Base deletion

Base substitute Base insert Base deletes

Different amino acid is New amino acids are New amino acids are
synthesised synthesised synthesised

Types of gene mutation Examples of disease
Base substitution Sickle cell anaemia
Base insertion Cystic fibrosis
Base deletion Thalassemia

Sickle Cell Anaemia

1. Caused by a gene responsible for the synthesis of haemoglobin.
2. Red blood cells of a patient are in the shape of a crescent
3. Because the red blood cells are not properly formed
4. Some red blood cells are normal whereas the rest are crescent shape

Normal shape red blood cell Crescent shape red blood cell

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Albinism

1. An individual who experiences albinism is an albino
Due to the mutation of a gene
Responsible for producing pigments of skin, hair and eyes

2. Pigments are not produced in the albino

Chromosomal Mutation
1. Involves changes to chromosomal structure or changes to the chromosomal number

Which can change the characteristics of an organism
2. Changes in chromosomal structure involve changes to the gene sequence in a

chromosome
3. Structural change causes abnormality to the chromosome

Known as chromosomal aberration
4. Types of chromosomal aberration include;

Deletion
Duplication
Inversion
Translocation

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Deletion

A part or a segment of chromosome is deleted or lost (loss of a few genes)
The new chromosome has less genetic material

Duplication

A part of a chromosome is copied which causes repetition of gene sequence
The new chromosome has extra genetic material

Inversion

A segment of chromosome is reversed end to end at 180o
rejoint at the same location (change in DNA sequence of chromosome).

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Translocation
Part of the chromosome is cut
Then join to another non-homologous chromosome.

1. A change in chromosomal number causes a diploid organism to;
Lose one or more chromosomes, or gain one or more chromosomes
Occurs when homologous chromosomes fail to separate during anaphase I in
meiosis
Or occurs when sister-chromatids fail to separate during anaphase II in meiosis

2. Caused by normal spindle fibres fail to form during meiosis
Known as nondisjunction
Causes abnormality in the number of chromosomes and in a gamete

3. Gamete may lose one or more chromosomes or gain one or more chromosomes

Meiosis I

Meiosis II

n+1 n+1 n-1 n-1 n+1 n-1 n n
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4. Abnormality in the number of chromosomes can be due to nondisjunction during
spermatogenesis or oogenesis

5. Fertilisation that involves abnormal gametes will produce a zygote that develops into an
individual with abnormal characteristics

6. The individual experiences change in phenotype

Nondisjunction of sex Nondisjunction of sex
An abnormal chromosome during oogenesis chromosome during spermatogenesis

XX

XX

XX

XO OY XXY XXX XO XXY

Turner Zygote Klinefelter Triple X Turner Klinefelter
syndrome dies syndrome syndrome syndrome syndrome

female male female female male

1. Write a possibility of sex chromosome in a zygote produces after fertilization is completed
2. Name the genetic disease suffered by a zygote

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Abnormalities In Autosomes

Diseases Chromosome number Characteristics of diseases

Down (2n + 1) = 47 An individual (male or female) has;
Syndrome Has three number 21 chromosomes Slant eyes
Flat nose
Protruding tongue
Broad forehead
Usually mentally retarded

Cri du chat Has normal chromosome number The cry of affected infants is similar to
syndrome Partial deletion on the short arm a meowing kitten
of chromosome number 5. Shows delayed development
Has mental and physical retardation.
o Structure of chromosome Most patients die during childhood
changes

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Abnormalities In Sex Chromosomes

Diseases Chromosome number Characteristics of diseases

Klinefelter (2n + 1) = 47 A sterile man with small testes that
Syndrome 44 + XXY fail to produce sperms
Possesses voice and chest similar
to those of a woman
Has long legs and hands.

Jacob (2n + 1) = 47 Male who is taller than normal
Syndrome 44 + XYY has problem with pimples on his
face
Turner (2n - 1) = 45 Slow in acquiring speech and has
Syndrome 44 + XO learning disability
Possesses weak muscles
(hypotonia).

Sterile female with lack of
secondary female characteristics
undeveloped breasts and ovaries
Weblike neck and low IQ.

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Mutation of Somatic Cells and Gametes

Differences Between Mutation in Somatic Cells and Gametes

Aspect Mutation In Somatic Cells Mutation In Gamete
1. Cell involve
Involves somatic cells such as skin Involves germ cell that produces
cell and eye cell gamete (Secondary oocyte or
sperm)

2. Inheritance Cannot be inherited by the next Can be inherited by the next
generation generation

3. Present of Disease is present only in the Disease is present in the individual
disease individual with the mutation with the mutation and is also
inherited by his/her descendants
4. Examples Example: Disease related to
nervous system Example: All inherited diseases
such as thalassemia

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