Kromosom adalah panjang, dan mempunyai struktur seperti bebenang

halus yang terdapat didalam nukleus .

Kromosom mengandungi deoksiribonukleik asid(DNA) dan protein.

Sel somatik(badan) manusia mempunyai 46 kromosom iaitu 22 pasang

autosom dan satu pasang kromosom seks autosomes .

Terdapat dua jenis kromosom iaitu autosom dan kromosom seks.

Mengandungi dua jenis kromosom seks , kromosom XY bagi lelaki dan

kromosom XX bagi perempuan .

KROMOSOM

KROMOSOM SEKS AUTOSOM

Are hereditary material located on chromosomes.

Mengandungi bahan DNA yang berfungsi untuk menurunkan

maklumat keturunan dari satu generasi ke generasi lain.

Gen menentukan sifat-sifat seperti ketinggian, warna rambut ,cap

jari dan rupa paras . Gen wujud dalam berpasangan.

PEMBAHAGIAN SEL

MITOSIS MEIOSIS

SEL SOMATIK GAMET

SEL KULIT

SEL TANGAN

SPERMA

OVUM

Contoh

Berlaku didalam Berlaku semasa pembentukan

contoh

terbahagi kepada

Mitosis adalah proses pembahagian sel yang menghasilkan

dua sel anak dari satu sel induk .

Dalam manusia ,mitosis hanya berlaku dalam sel somatik

(sel badan) kecuali sel pembiakan . Pada tumbuhan ,mitosis

berlaku pada hujung akar dan pucuk.

Menghasilkan sel baru untuk pertumbuhan dan mengantikan sel

yang mati, tercedera dan lama.

Untuk menurunkan bahan genetik dari sel induk kepada anak melalui

pembiakan

Untuk memastikan sel baru yang mempunyai bilangan kromosom

yang sama dengan bilangan kromosom sel induk

Both the new cells will have the same number of chromosomes

and genetic content as the parent cell.

Kromosom menjadi pendek , tebal dan

menjadi jelas kelihatan.

Setiap kromosom mengandakan

dirinya dan membentuk dua kromatid .

Membran nukleus hilang

Setiap kromosom akan tersusun

ditengah khatulistiwa dalam satu

barisan .

Gentian gelendong akan terbentuk .

Kromatid terpisah dan bergerak

kekutub bertentangan sel .

Pada masa yang sama , sel mula

membahagi .

Dua sel anak terbentuk .

Membran nukleus yang baru

terbentuk .

Dua sel anak mempunyai

kandungan genetik yang sama

dengan induk.

Meiosis adalah proses yang menghasilkan empat sel anak dari satu

sel induk. Berlaku hanya didalam organ pembiakan.

In humans and animals ,occurs in the testis or ovary. In plants,

occurs only in the anther and ovary

The number of chromosomes in a gamete has only half the

number of chromosomes in the parent cell.

To produce gametes.

To ensures that each gamete has only half the number of

chromosomes of the parent cell .

Causes genetic variation among the same species .

Chromosomes in the nucleus shorten

and thicken .

Replication and crossing over occur

occur on chromatids.

The chromatids exchange segments .

Chromosomes arranged in the centre

of the cell .

The nucleus membrane disappears .

Spindle fibre formed .

Chromosomes separate and move

to opposite poles of the cell.

The cell begins to devide into two.

Two daughter cell formed.

The nucleus membrane reforms.

Chromosomes are arranged in

the centre of the cell.

The nucleus membrane disappears.

The chromatids separate and

move to opposite poles of the

cell .

The cell begins to divide .

The nucleus membrane reforms.

Four gametes are formed.

Each gametes contains half of

the number of chromosomes in

the parent cell.

All of them have different genetic

information (shows variation ).

Two daughter cells are produced Four gametes are produced

Cell division occurs once

Cell division occurs twice

Number of chromosomes in the

daughter cell is the same as the

parent cell .

Number of chromosomes in the

daughter cell is half of that in the

parent cell

Crossing over does not occur

Crossing over occurs

Occurs in all somatic cells

( body cells )

Occurs only in the reproductive

organs.

Dominant genes are genes which show clearly the characteristics

when paired with a dominant gene or a recessive gene.

Recessive genes are genes which only show the characteristics when

these genes are paired with another recessive gene .

Genotype refers to the genetic information of an organism.

Phenotype refers to the physical appearance that can be seen in an

organism.

If a tall person has ` TT ` gene .

TT ----- it is a genotype

Tall ----- it is a phenotype

TT tt

T T t t

Tt Tt Tt Tt

Tall plant (pure breed) Dwarf plant (pure breed)

Parents

Gametes

Fertilisation

First

generation

Meiosis

Tall Tall Tall Tall

Tall trait is controlled by the dominant gene ,

dwarf trait is controlled by the recessive gene

Tall plant (hybrid) Tall plant (hybrid)

Tt

TT

T t T t

Tt

tt Tt Tt

F1 generation

Meiosis

Gamete

Fertilisation

Second

generation

Ratio of genotype

Ratio of phenotype

Tall Tall Tall Dwarf

¼ or 25% ¼ or 25% ¼ or 25% ¼ or 25%

3 tall 1 dwarf :

:

1. A right-handed man(Kk)marries a left –handed woman

(kk),determine the probability of their child being born left-handed.

[ K:dominant gene(dominant) ; k : recessive gene(left-handed )

Determination of left-handed in human beings

Genotype of

offspring kk kk Kk Kk

K k k k

kk Kk Parents

meiosis

Gametes

fertilisation

Phenotype of

offspring

Right-handed Right-handed left-handed left-handed

Sex chromosomes determine the sex of a person . Each ovum contains ( 22 + X ) chromosomes .

Each sperm contains ( 22 + X ) chromosomes or ( 22 + Y )

chromosomes .

If a sperm that carries the Y chromosomes fertilises an ovum, the

zygote is a male.

22 + Y X 22 + X 44 + XY

Sperm ovum Male zygote

If a sperm that carries the X chromosomes fertilises an

ovum , the zygote is a female.

Female zygote Sperm ovum

22 + X

22 + X 44 + XX X

mensenyawakan

44

+

XY

44

+

XX

44

+

XY

22

+

X

22

+

Y

22

+

X

22

+

X

44

+

XX

44

+

XX

44

+

XY

Gamete

Offspring

Ratio

Parents

Father Mother

X

50 % female 50 % male

Meiosis

Fertilisation

One zygote is formed

and undergoes mitosis

Ovum Sperm

Only one ovum is

released by the ovary

Only one sperm

will fertilise this

ovum

The zygote divides into

two. Two embrios

develop in the uterus .

The feotuses become

fully developed and are

born as identical twins.

The identical twins are

either two boys or two

girls .

The ovary

produces two

ova at the

same time.

These ova are

fertilised by two

sperm cells .

Two zygotes will

develop from these

fertilised ova.

Two embryos will

develop in two

separate placenta.

A non-identical twins

are born.They may be

both boys or both girls

or a boy and a girl.

Ovum Zygote Embryo Foetus Child

One sperm will fertilise one ovum

and one zygote is formed.

They share one placenta

in the mother`s uterus.

Two sperms will fertilise two ova

and two zygotes are formed.

They do not share placenta and

grow in separate placentas in the

mother`s uterus

They have the same sex.

Both males or females

They may have the same or

different sexes. Both females ,

both males,one male and one female

They have the same genetic content,

ex: same appearance and similar

characteristic features.

They have different genetic content

ex : different appearances

The single zygote divides into

two zygotes The two zygotes formed do not

divide.

OVUM ZYGOTE EMBRYO FOETUS CHILD

Only one

ovum is

released by

the ovary .

Only one sperm will fertilise

this ovum. Developing

embryos begin to split into

two identical twin.

The development of the

identical twins stop partway

Two babies are born

conjoined at childbirth.

They may share certain organs like brain,stomach or heart .

They may be joined to one another at the head, abdomen or breast .

Siamese twins are basically identical twins which are joined

together because the zygote failed to divide completely into two

separate embryos.

Mutation is the spontaneous change to the structure of genes or

chromosomes of an organism. Its can causes change of

characteristics in a child.

Occurs in somatic cells or in gametes and will be inherited by one

generation to another.

MUTATION

GENE

MUTATIONS

CHROMOSOME

MUTATION

Divided into

Albinism

Haemophilia

Colour blindness

A change occurs in chemical composition of the

gene which controls the formation of red blood

cells.

Thalassaemia

The baby with thalessemia lacks haemoglobin.

Caused by the change in the genes that

produce haemoglobin .

Sickle cell anaemia

Normal red blood cells

Sickle –shaped red blood cells

Involve changes in the chemical composition of genes.

Genes that have undergoes mutation are called mutants.

- is caused by the change in the gene that controls skin colour .

The skin and hair of albinos are white and their eyes are brown.

A colour blind person cannot see or differentiate

the colours red and green.

- the blood lacks a certain protein which necessary for it to clot .

- is a sex-linked(terangkai seks) disease determined by a recessive

gene on the X chromosomes .

Changes in the structure or number of chromosomes or arrangement

of genes in chromosomes.

A chromosomes break away and

go missing. The number of

chromosomes can be decreased.

Inversion of genes

Some genes are inverted .

Is caused by the presence(kehadiran) of one extra chromosomes at

chromosomes 21 in the somatic cells .A patient has 47 chromosomes in

the body cells.

Slanting eyes ,mentally retarded ,short fingers , stunted growth , a weak

heart , a poorly developed brain and small mouth but big tongue .

Is caused by an extra X- chromosome .

The man has three sex-chromosomes,consisting of two X-chromosomes

and one Y-chromosomes , which is XXY .

The man has 47 chromosomes and has small testes , fails to produce

sperm and narrow shoulders .They are infertile .

A person who suffers from this hereditary disease lacks one X –

chromosome in the body cells .

They have only one sex chromosome which is XO .

Normally , females suffer from this hereditary disease .

The woman has small breasts , infertility , short and does not

menstruate .

Chemical substances like pesticide ,nicotine,drugs,colouring and

artificial sweetener.

Radioactive radiation such as gamma ray can affect growth and cell

division .

Ultraviolet ray and X- rays can cause skin cells to mutate and cause

skin cancer .

Temperatures which are too high or low can also cause mutation .

Mutation causes variations in organisms which allow them to adapt

to the environment

Species that are more resistant to diseases, weather and polluted

environment can be produced

Mutations cause diseases like colour blindness and haemophilia

which cannot be cured .

Sometimes ,diseases like haemophilia and sickle-cell anaemia

can cause death .

Klinefelter`s syndrome causes infertility.

Mutation causes physical , mental and foetus retardation .

Improving the quality of breeds through selective breeding .

Bringing in new species with higher resistance to diseases or pests .

Obtaining the production of large quantities of crops and livestock in

the shortest time .

Oil palm ( Tenera )

The characteristics are :

More fruit, its kernel contains more

oil and have thinner shell with

more content .

After mutation Before mutation

More fruits , ripen faster and are

more resistant to dry season .

Characteristics of hybrid .

Fruits are sweeter

and have more

content .

Fruits are

sweeter, bigger

and more

resistant to

disease and dry

season .

Exotica Papaya

SHEEP

MAIZE

New breed (Malin-X) is bigger in size, matures faster,

supplies better quality meat and wool .

Characteristics of new breed

The hereditary disease like colour blindness,albinism are caused by

recessive genes .

Genes are normally passed down by females who are the carrier to

their children.

A male will suffer from this disease if he has one recessive gene .

These are genes which are present in the X chromosomes but not in

the Y chromosomes.

Example

A woman carrier of colour blindness (XXb ) marries a man with normal

vision (XY). Determine the probability of their child being born as a

(a)Normal girl .

(b)Normal girl but a carrier .

(c)Normal boy.

(d)Colour blind boy . [ Xb : recessive gene of colour blindness ]

XY

X Y X

XXb

XX

Xb

XY XXb XbY

Man ( Normal ) Woman(carrier)

Parents

Gametes

Fertilisation

Characteristic

of offspring

Genotype of

offspring

Normal

girl Normal girl

but a carrier

Normal

boy

Colour

blindness boy

X

Meiosis

(a)Normal girl is ¼ or 25 %.

(b)Normal girl but a carrier is ¼ or 25 %

(c)Normal boy is ¼ or 25 %

(d)Colour blindness boy is ¼ or 25 %

Probability of having a

VARIATION Is the differences in characteristics

which exists among individuals

of the same species.

CONTINUOUS

VARIATION

DISCONTINUOUS

VARIATION

Divided into

Is variation which does not show obvious in a trait among individuals

of the same species .

For examples : Weight , colour of the skin , colour of the hair .

Nu

mb

er

of

stu

den

ts

Weight (kg)

21-

25

26-

30

31-

35

36-

40

41-

45

46-

50

51-

55

56-

60

2

4

6

8

Skin colour

It is influenced by genetic factors and environmental factors such as

weather, or food.

Is variation which show obvious and definite in a trait among

individuals of the same species .

For examples : blood group , ear lobe, fingerprint , ability to roll

the tongues , left-handedness ,sex and presence of dimples .

Eye colour

Can roll tongue

fingerprint

Discontinuous variation is influenced by genetic factors .The

characteristics of discontinuous variation are permnent .

With ear lobe Without ear lobe

black brown

Blood group

CONTINUOUS

VARIATION

Types of variation

DISCONTINUOUS

VARIATION

Inherited from parents and continue to be inherited

by future generations . This variation is permanent .

Influenced by environmental characteristics such as

diet, sunlight and weather . This type of variation

can change .

Allows formation of new species that have better qualities to

adapt to changes in the environment .

Allows the same species to differentiate from one another .

In plants , variation like resistance to pathogens such as bacteria

and fungi enable the plants to grow rapidly and reproduce quickly .