Chapter 5 (Mitosis)

7/27/2019 Chapter 5 (Mitosis)

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CELL DIVISION

CHROMATID

All the chromosome in the nucleus ofsomatic cell exist in pairs and call as diploid

number of chromosome (2n)

In humans, one set of chromosome consists of23 pairs of chromosome . That means our somatic

cell have 46 chromosome .

From 23 pairs of chromosome, one pairs is thesex chromosome .

Two X chromosome (XX), referred to female ,while XY chromosome referred to males

THE HUMAN CHROMOSOMES

WHY CELL DIVISIONSIMPORTANT

To replaced the dead or damaged cell with new cells.

Increase the number of cell in the body for growing

To maintain chromosomal number of each organisms

THE CELL CYCLE

Interphase M phase Cytokinesis.

(Cytoplasmicdivision)

Interphase is also the stage at which cells growlarger and prepare for cell division

During interphase, the nucleus is big and well difined.

Interphase is divided into three shorter stages orsub-phases:

(a) G1 phase (growth phase 1)

(b) S phase ( DNA synthesis)

(c) G2 phase (growth phase 2)

MITOSIS

Mitosis is process division of nucleus in thesomatic cell.

Mitosis can be subdivided into four phases, namely :

(a) Prophase(b) Metaphase(c) Anaphase

(d) Telophase

The number chromosome are same likethe parents cell

PROPHASE• Nuclear membrane begins to disappear.• Chromatin threads coil up to form chromosomes• Centrioles move to the opposite poles as spindle

fibers form between them.

METAPHASE• Nuclear membrane disappears.•

Spindle fibers surround the chromosomes• Chromosomes move towards the equator and

become attached to the spindle microtubules

by their centromers

ANAPHASE• Centromeres split .• The two chromatids from each chromosomes

move to the opposite poles at the spindles contract.

TELOPHASE• Spindle fibers dissapear• A new plasma membrane forms around each group

of daughter chromosomes• Inside each daughter nucleus, the chromosomes

uncoil and form chromatin.• Formation of cleavage or cell plate for cytokinesis

begins

CYTOKINESIS• The division of cytoplasm of a cell to form new

cells after the dauhgter nuclei have been formed• In animal cells, cytokinesis take place with the

formation of cleavage furrow• In plant cells, cytokinesis take place with the

formation of cell plate

THE FUNCTION OF MITOSIS

• To produce new cells for growth

• To replace millions of cells which die or are

worn out• To develop zygotes in sexual reproduction

REGENERATION

Lizard drop a tail to entice a predator Healing of woundsSome plants capable of total regeneration(the formation of a whole new plant from aleaf, stem or root)

THE IMPORTANCE OF CONTROLLEDMITOSIS

For the normal cellgrowth

For the normaldevelopment

For maintain the numberof cell in body

THE EFFECTS OF UNCONTROLLEDMITOSIS

Cancer Tumor• Cancerous cell divide freely and

uncontrollably.• Cancer can be caused by:

- damage to the DNA- mistakes that occur in the genes

that controlled cell division.- the effect of radiation- carcinogen compounds.

• Form by cancerous cellthat is divideduncontrollably

UNCONTROLLED MITOSIS

Will produce cancer cells

NORMAL CELLS

CANCERCELLS

- Divide freely anduncontrollably withoutheeding the cell cyclecontrol system

CAUSES OF CANCER

1. Damage to the DNA2. Mistakes that occur in the genes that control

cell division

3. The effects of ionising radiation such as X-rays, UV-rays4. Certain chemical compounds like tar in

tobacco

5. Carcinogenic compounds such asformaldehyde.

THE DIFFERENCES BETWEEN NORMALCELLS AND CANCEROUS CELLS

1. Normal cells undergo controlled growth butcancerous cells undergo uncontrolled growth.

2. Normal cells have a single organised layer but

cancerous cells have multi-layered anddisorganised cells3. Cells are differentiated and carry out specialised

functions in normal cells but in cancerous cells they

undifferentiated and do not have specialisedfunctions.

4. The nuclei and chromosome number of normal cellare normal but the nuclei and chromosome number of cancerous cells are abnormal.

Test Your IQ

1. Give the definition of mitosis2.State two reasons why mitotic cell division is

important in living organisms.3. Name the stages in M phase4. State the important events that occur at

(i) G1

phase(ii) S phase(iii) G2 phase

THE APPLICATION OF KNOWLEDGEON MITOSIS IN CLONING

Cloning Tissue culturetechnique

ANIMAL CLONING

CLONING

Cloning is the process of producing clones ofa cell, tissue or organism, through asexual

reproduction

Animals cloning involves the transfer of the

nucleus from a somatic cell to an ovum orembryonic cell which has the nucleus removed

Many animals have been succesfully cloned eversince the first mammal, a sheep named Dolly

Cloning…….

advantages

Cloning offers the opportunity to rapidlyimprove the genetic makeup of a herdthrough reproduction of elite animalsAs cloning techniques become more

efficient, more clones are living to adult ageand so their reproduction function can bestudied. It appears that there is no differencein the health of cloned animals compared withnon-cloned animals.Cloning allows the reproduction of animalsthat have been genetically modified (eg for the production of medicines in milk).

WHAT ARE THEDISADVANTAGES OFCLONING?

1. Losing genetic diversity2. Wiping out entire population. – at risk from

new pathogens / diseases3. Inbreeding – because everyone has the

same genetic materials, causes morediseases, abnormalities eventually death tothe population.

Bermulanya perkembangan manusia (1)[Mitosis]

Dia menciptakan kamu dari diri yang satu (Adam),kemudian Dia menjadikan daripadanya, isterinya(Hawa) dan Dia mengadakan untuk kamu binatang-

binatang ternak lapan ekor: (Empat) pasangan(jantan dan betina). Dia menciptakan kamu dalamkandungan ibu kamu (berperingkat-peringkat) darisatu kejadian ke satu kejadian) . Dalam tiga suasanayang gelap-gelita. Yang demikian (kekuasaanNya)ialah Allah Tuhan kamu; bagiNyalah kekuasaanyang mutlak; tiada Tuhan melainkan Dia; oleh itubagaimana kamu dapat dipesongkan (darimematuhi perintahNya)?[Az zumar: 6)

TISSUE CULTURE TECHNIQUE

Tissue culture technique involves the growth ofcell or tissues outside the cell in a suitable culture

medium which contain nutrient and growth hormoneor through in-vitro methods.

New individuals that are produced, are generally

identical to the existing organisms

The cultures medium are incubated at an optimaltemperature of 37 0C and at optimal pH

Advantages of Cloning

1) Many clones are produced in a short time

2)The good qualities of the plants and animals can

be selected and maintained in the clones.3) It increase the quality of products.

4) It ensures the continuity of hereditary traits

from the parent to the clones.

5) It can be carried out any time of the year.

MEIOSIS

Meiosis is process division of nucleus in theReproductive organ.

This process will reduce the number of chromosomein daughter cell to half that of the parent

Each gametes receive only one chromosome fromevery pair of homologous chromosomes.That means in human gametes, contain 23 haploid

chromosome

During the fertilization, sperm and egg will meet,restore the complete number of chromosome and

genetic material, forming a diploid zygote with46 chromosome

In multicellular organisms, meiosis occurs in thetestes ( in males) and ovaries (in female)

In plants, it occurs in anthers (males) and ovaries(female)

Meiosis

Meiosis I Meiosis II-Prophase I-Metaphase I-Anaphase I-Telophase I

-Prophase II-Metaphase II-Anaphase II-Telophase II

Interphase

• The cell replicates its DNA and duplicates itschromosome

• The cell now has twice the amount of geneticmaterial, but the same number of chromosome

as before• The nucleus membrane and nucleolus are still present

In animal cells a pair of centrosomes is also formedin the cytoplasm

Meiosis 1

Prophase 1 Metaphase 1 Anaphase 1 Telophase 1

• The chromatids of homologous chromosome,cross over along their length and at this point it

called as chiasmata.• At this point, there is a change in genetic materialbetween the non-sister chromatids. This processwill form new combination of genetic material andthis important for genetic variation

The nuclear membrane and nucleolus disintegrateand the spindle fibres are formed

Metaphase 1

Paired homologous chromosome line up at themetaphase plate.

One chromosome of each pair faces each pole ofthe cell

The chromatids of each chromosome are attachedto the spindle fibres at their centromer

Anaphase 1

• The pair of homologous chromosome separatefrom one another and move to the opposite poles

• Each chromosome moves with its centromereheading towards the pole and the two sister

chromatids trailing behind

T l h 1

Telophase 1

The chromosome arrive at the poles.• Each pole now has a haploid daugther nucleusbecause it contain only one set of chromosome

• The spindle fibre disappear• The nucleus membrane reappears to surround

each group of chromosome• The nucleolus then reappears in each nucleus

Cytokinesis occurs. The cleavage form and twohaploid daughter cells form

Between meiosis I and meiosis II, there is little orno interphase and no replication of chromosome

Meiosis II

Prophase II

Metaphase II

Anaphase II

Telophase II

Metaphase II

Chromosome line up at the metaphase plate

Each sister chromatid is attached to the spindle

fibre at the centromere

A h II

Anaphase II

The centromers holding the sister chromatidstogether split

• Chromatids separate

• Spindle fibre pull each chromatids to oppositepoles

Telophase II

Finally the nucleoli and nuclear membrane re-form.

• The spindle fibres break down

• Cytokinesis follows and four haploid daughter cellare formed. Each haploid cell contains half the

number of chromosome. The haploid cell becomegametes

Meiosis I Meiosis II

Meiosis I Meiosis IISimilarities

• Both process consist 4 stage.• Both process involve nucleus and cytoplasm division

Meiosis I Meiosis II

Meiosis I Meiosis IIDifferences

• Synapsis occur

• Crossing over occur

• No synapsis

• No crossing over• In metaphase I, pairedhomologous chromosomeline up at the metaphase

• In metaphase II,chromosome line up at

the metaphase plate

• In telophase I, twohaploid chromosome

are formed

• In telophase II, fourhaploid chromosome

are formed

Mitosis Meiosis

Mitosis MeiosisSimilarities

• The process of cell division in which DNA replicatesonly once

Mitosis Meiosis

Mitosis MeiosisDifferences

• All somatic cell

• Replace damageand dead cell

• Reproductive organ

• Produce gametes

• Synapsis notoccur

• Synapsis occur

• Crossing overnot occur

• Crossing overoccur

Place occurs

Purpose

Synapsis

Crossingover

Mitosis Meiosis

• Produce cell forgrowth and repair

• Not causegenetic variation

• Produces gamete

• Cause geneticvariation

• One • Two

• Two daughtercell

• Four daughtercell

Genetic

variationNumber of

division

Number ofdaughter

Mitosis Meiosis

• Same as theparent cell

• Diploid

• Different fromthe parent cell

• Haploid

Geneticcontent

Chromosomalnumber of

daughter cell

THE IMPORTANCE OF MEIOTIC

THE IMPORTANCE OF MEIOTICCELL DIVISION

Ensure the maintenance

of diploid numberof chromosome

Provides geneticvariation

Leads to geneticrecombination

Appreciating the Movement of Chromosome

Appreciating the Movement of Chromosomeduring Mitosis and Meiosis

• The meiosis and mitosis ensure the survival ofeach species from one generation to the next.

Asexual reproduction through mitosis processproduces offspring that are identical to singleparent

Sexual reproduction through meiosis processproduces genetic variation in the offspring

Chapter 5 (Mitosis)

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