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
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
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
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 .