5.1 mitosis

IZAT EZATTE BINTI MUSA4 UTM

THE NECESSITY FOR THE REPRODUCTION OF NEW CELLS ORGANISMS.Mitosis is the process of cell division that produces

two daughter cells which are genetically to each other and to their parent cell.

The significance of mitosis in living things: Repair and replace the damaged or dead cells Increases the number of unicellular organisms. Ensures that new cell are genetically identical to the

parent Preserve the diploid number of chromosomes

Increases the number of cells in individuals(single-celled

organisms) Aids in growth process(multi-celled organisms)

The phases in the cell cycleCell cycle-the life of a cell from the time it is

produced until it completely divides into two new daughter cells.

Activity of the cell during mitotic division:Preparing for the divisionProduce cytoplasm and organelles-formation of

daughter cells.Two major phases:

InterphaseMitotic cell division(M Phase)

Phase in Cell cycle

InterphasePHASE DESCRIPTIONS

G1(FIRST GAP) •The size of cells increases •RNA is produced•Synthesise protein and new organelles•Chromosome cannot be observed clearly and known as chromatin

S(SYNTHESIS) •DNA synthesis•The DNA replication takes place•The copied chromosomes contain two sister chromatids which are identical

G2(SECOND GAP) •Cell preparing for division(mitosis)•The cell grows,produces organelles,protein and membrane•Nucleus is well-defined•Chromosome duplication completed•DNA loosely packed in long chromatin fibres

1. Interphase This is the resting or

non-mitotic of the cell cycle

It comprise G1,S and G2 stage of the cell cycle

DNA is replicated during the S phase of interphase

The M phase(mitosis and cytokinesis) PROPHASE

If the first stage of mitosis The chromosomes

condense and become visible

The centrioles form and move toward opposite ends of the cell(the pole)

The nuclear membrane dissoves and the mitotic spindle thread is formed(from the centrioles)

Spindle fibers from each centriole attach to each sister chromatid at the kinetochore

Chromatids are connected at the centromere

METAPHASEThe chromosomes lined

up on the cell equator which is the metaphase plate

The spindle fibres are formed completely

ANAPHASESpindle attached to

kinetochores begin to shorten

This exerts a force on the sister chromatids and pulls them apart

Spindle fibres continue to shorten,pulling chromatids to opposite poles of the cell

Early anaphase

Late anaphase

TELOPHASE

Both chromosomes have reached the opposite poles

The chromosomes decondensed

The nuclear enveloped is formed

Nucleus reformedThe spindle fibres

dissappearOnce separate,the

chromatds are again called chromosomes

Two daughter nuclei are formed with identical set of chromosomes

CytokinesisCytokinesis is the process of the cytoplasm division

after the separation of chromosomes

CYTOKINESIS IN PLANT CELL

•The vesicles move to the equator between the two nuclei and fuse to form two membranes that become cell plate

•The cell plate grows upwards•The new cell wall is laid down between membranes and fuses with the existing cell wall

CYTOKINESIS IN ANIMAL CELLS

The vesicles move to the equator between the two nuclei and fuse to form two membranes that become cell plateThe cell plate grows upwardsThe news cell wall is laid down between membranes and fuses with the existing cell wall

The importance controling mitosisTo ensure that organism can function

properlyTo ensure that organisms can grow and

develop normallyTo help in repairing damage cells and

tissues for the survival of life

The effects of uncontrolled mitosis in living things

It due to the changes of gene which control the cell cycle e,g:The growth of cancerous cell

Cancerous cells could lead to the death of the organism if it is not prevented from invanding and destroying neighbouring cells

This condition can be caused by certain virus,toxic chemical susbtances

The cells divide very fast and unregulated.(Tumour) Benign tumour-Abnormal cells that remain at the original site

and be removed by surgery Malignant tumour-becomes invasive and spreads to

neighbouring tissues and cells (cancer)

The application of knowledge on mitosis in cloning Production of genetically identical individuals

Cloning of sheep

Producing genetically identical organisms which carry a useful gene

A piece of DNA carrying a gene of interest and a gene for antibiotic resistance

The cells is grown on a medium containing the antibiotic so that only the cells with the inserted DNA will survive

The nuclei from surviving cells is inserted into unnucleated egg cells

The egg cells is implanted into the surrogate mother Clone which carry the useful gene are born

Application of cloning technology is important to:

Produce genetically identical organs for transplantation

Produce human tissuesRepopulate endangered species

The advantages and disadvantages of cloning

Advantages Ensure the continuity of hereditary traits from the parent to the clonesIncrease the rate of production and the quality of the productsGood qualities of the plants and animals can be selected and maintained in the clonesMany clones are produced in a short timeCan be carried out any time of the year

DisadvantagesRaise ethical issues on human The resistance of the clones towards diseases and pests is the same.If a clone is infected with a disease or attacked and die

Raise ethical issues on human cloning