Prepared by :

En. Muhd Fazli b. Dollah

SP Integrasi Gopeng

LEARNING OUTCOMES•To state the necessity for

the production of new cells in organisms,

•To explain the necessity for the production of new cells identical to parent cells,

•To state the significance of mitosis,

•To identify the phases in the cell cycle,

MITOSIS• A type of cell division which

involve the division of the nucleus to produce two daughter cells, each contain same number & same kind of chromosome as the parent cell

• Occurs in all somatic cells except gametes.

• In unicellular organisms – for asexual reproduction. (Amoeba sp.)

• Multicellular organisms – to generate new cells to replace dead & damaged cells, for growth & development

• Somatic cells contain 2 sets of chromosomes, 1 set from female parent, 1 set from male parent –diploid(2n)

• Single set of unpaired chromosome – haploid (n)

• Each somatic cells produce 2 new diploid cells identical to the parent cell

Examples number of chromosomes

ORGANISM SOMATIC CELL (2n)

GAMETE CELL (n)

Human 46 23

Camel 70 35

Goat 60 30

Porcupine 34 17

Bat 44 22

Squirrel 40 20

House fly 12 6

Chicken 78 39

Alligator 32 16

Mosquito 6 3

Pea 14 7

Rice 24 12

SIGNIFICANCE OF MITOSIS

• For growth, repair & replaces cells that are dead or damaged

• A form of asexual reproduction to increase the number of organisms

• To ensure that the offsprings/new cells are genetically identical to the parent.

• Preserves the diploid number of chromosomes

The Cell

Cycle

INTERPHASE (G1, S, G2)

G1 : Growth phase 1

The cell growth by producing proteins & cytoplasmic organelles

S : Synthesis

Synthesis of DNA, chromosomes are duplicated & DNA has replicated to form 2 identical sister chromatids joined together by centromere

G2 : Growth phase 2

Cell growth & cell differentiation occur

M PHASE(Cell Division)

Mitosis : nucleus divides

Cytokinesis : division of cytoplasm

LEARNING OUTCOMES•To explain the process of

mitosis & cytokinesis,

•To arrange the various stages of mitosis in the correct sequence,

•To compare and contrast mitosis & cytokinesis in animal cell & plant cell

STAGE OF MITOSIS

• Divided into four phase : PROPHASE, METAPHASE, ANAPHASE & TELOPHASE

• Nucleus divides cytokinesis (cytoplasm divides)

PROPHASE• Centrioles move apart to

opposite poles

• The chromosomes coil up, condense & shorten

• Two identical chromatids (sister chromatids) appears, attached at centromere

• Nuclear membrane breaks down

• Nucleolus disappears

• Spindle fibres begin to form extend between the centrioles.

METAPHASE

• The chromosomes move to the cells equator

• The chromosomes line up along the equator of the cell with the centromeres attached to the spindle fibres

• Each chromatid of the chromosome faces its own pole

• Metaphase ends when the centromeres divide

ANAPHASE • The centromere of each chromosome divides into two

• The sister chromatids of each chromosome separate and move to opposite poles of the cell

• The spindle fibres pull the centromere toward each pole with the chromatid arms trailing behind

• When the chromatids reach their respective poles, the chromatids become independent chromosomes.

TELOPHASE

• Final stage of mitosis

• Two sets of chromosomes, one at each pole

• Chromosomes start to uncoil & revert to their extended state.

• Less visible under the microscope

• Spindle fibres begin to disappear

• Nuclear membrane begin to form around each chromosomes. 2 daughter nuclei are formed

• Cytokinesis occurs at the end of telophase

CYTOKINESIS• The division of cytoplasm.

• Animal cell = actin filaments in the cytoplasm contracts to pull a ring of the plasma membrane inwards to form a cleavage furrow the cell is separated into 2 daughter cells.

• Plant cell = starts with the formation of cell plate at the equator of the cell cell plate enlarge new cell wall is formed 2 daughter cells are produced.

OVERALL PROCESS OF MITOSIS

LEARNING OUTCOMES• To explain the importance of

controlled mitosis,

• To explain the effects of uncontrolled mitosis in living things,

• To describe the application of knowledge on mitosis in cloning,

• To explain the advantages & disadvantages of cloning.

REGULATION OF THE CELL CYCLE

• Cell cycle is controlled by genes of the chromosomes

• Each type of cell has its own timing & rate of cell division (controlled mitosis)

• Uncontrolled mitosis happen when the genes that regulate the cell cycle is mutated or damaged

• May be caused by too much exposure to carcinogens (cancer-causing agent).

REGULATION OF THE CELL CYCLE

• Tumor : the number of abnormal cells produced increase very quickly

• Benign tumor : abnormal cells remain at the original site

• Malignant tumor : tumor becomes invasive & spread to neighbouring tissues, impairing the functions of one or more organs cancer

APPLICATION OF KNOWLEDGE ON MITOSIS IN CLONING

• To increase the quantity of the product

• To improve the quality, to produce new species & to ensure uniformity in the traits of the plants

CLONING• A natural process asexual reproduction of

unicellular organisms

• Contain same genetic content & chromosomal number with one another as well as with the parent organism

• CLONING : A TECHNIQUE / the process of

producing clones or genetically identical organisms through

asexually reproduction.

CLONING / GENETIC ENGINEERING

• A highly artificial form of asexual reproduction based on mitosis

• The offspring is produced by mitosis from a diploid cell

• The transfer of the nucleus from a somatic cell to an ovum or embryonic cell with the nucleus removed.

TISSUE CULTURE

• A technique in reproduction which involves the transfer of tissues or cells from an organism into a suitable culture medium to produce a whole new organism (identical to the existing organism) clone

AN OUTLINE OF PLANT TISSUE CULTURE

• Sterilised apparatus & materials The surface of a leaf is sterilised

with ethanol / dilute sodium hypochlorite solution Small pieces of tissue (explants)

culture medium a callus (an undifferentiated mass of tissue)

formed (mitosis) embryos plantlets transferred to

the soil adult plants

ADVANTAGES1. Produced in a short time (increase quantity)

1. The good qualities of the plants/ animals can be selected & maintained in the clones

1. Increases the rate of production & the quality of the product

1. Ensure the continuity of hereditary traits from parent to the clones

1. Can be carried out any time of the year

DISADVANTAGES1. The resistance of the clones towards

diseases & pests is the same. 1 infected with a disease/pests, all the clones will also affected. Lead to the extinction of the species.

2. Carried out under controlled environment. External environment changes, the will be destroyed

3. Prevents natural selection

4. No variation