mitosis krt baru

8/3/2019 Mitosis Krt Baru

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LECTURE 9:

MITOSIS AND CYTOKINESIS


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INTRODUCTION

1. Cell division is accomplished by MITOSIS = division of chromosomes and

CYTOKINESIS = division of the cytoplasm

2. Mitosisis the division of somatic cells in which

the appropriate number of chromosomes ismaintained

3. A somatic cell is a body cell of an organism ora cell that is not involved in reproduction of a

new organism. Somatic cells divide to recreatethemselves


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4. Cytokinesis is division of thecytoplasm to produce two daughter cells,usually begun during telophase

5. Difference between animals and plants:

plants are divided by the formation of acell plate (=pelat), where animal cells aredivided through the formation of a cellcleavage (=belahan). Cell plate

materials originate in the golgi complex.


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INTRODUCTION

4. When the somatic cell has its complete complement ofchromosomes it is said to be in the diploid condition

5. At the end of mitosis daughter cells are diploid

Terminology

Genome : cells genetic information

Somatic : body cells Gametes : reproductive cells (sperm and egg

cells)

Chromosomes : DNA molecules

Diploid (2n) : 2 sets of chromosomes Haploid (1n) : 1 set of chromosomes


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BASIC PRINCIPLECell Division: Key Roles


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Coordination of Mitosis and Cytokinesis

Cell Divisiondemandscoordination ofDNA replication(Mitosis) anddivision of thecytoplasm(Cytokinesis).

Cell Division atcellular level


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Whats so important about cell division?

Theprocess


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The Knit of Identity - Mitosis Precisely and EvenlyDivides Duplicated Chromosomes

Precisely dividing the duplicated chromosomes has the consequence ofproviding each new cell with an identical and complete set of geneticinstructions.

INTERPHASEPROPHASE

METAPHASE


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Mitosis Precisely and Evenly Divides DuplicatedChromosomes

Cytokinesis is the process of cell division and it is distinct and separablefrom mitosis.


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In Animal Cells,

a CleavageFurrow Formsand SeparatesDaughter Cells

Cleave furrow in a dividing frog cell.


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The Plant Cell Wall Forces Cytokinesis to Play byDifferent Rules


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Cancer

Transformation

Tumor: benign (=jinak) or malignant (=ganas)

Metastasis


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Cancer Is One Outcome of A Runaway Cell Cycle

Licentious division - prostate cancer cells during division.


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Chromosome and DNA

What is the difference between DNA andChromosome?What is Karyotype ?


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Cell Devision atchromosome level

CHROMOSOMEDUPLICATION

AND

SEPERATION


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DNA ReplicationSimple in Principle,

Complicated in Practice

Cell Devision at DNA

level


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DNA is Packaged into Chromosomes

The packaging is impressive 2 meters of human DNA fitinto a sphere about 0.000005 meters in diameter.

chromatin

duplicatedchromosome

DNA in the cell isvirtually alwaysassociated with

proteins.


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The Link Between DNA Replication and ChromosomeDuplication


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DNA is Condensed into Visible ChromosomesOnly For Brief Periods in the Life of a Cell

95% of the time,chromosomes are likethis.

Easily visible chromosomes areapparent perhaps 5% of thetime in an actively growing celland less in a non-growing cell.


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A normalhuman

karyotype

Boy orgirl?

Note that almost all chromosomes come in homologous pairs.

A Karyotype isan arranged picture of chromosomes at theirmost condensed State


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The Cell Cycle


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From Birth toRebirth, a CellProgresses

ThroughCharacteristicStages ThatConstitute the

Cell Cycle

In multicellularorganisms like us,

progress throughthe cell cycle iscarefullyregulated.


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The Cell Cycle1. Interphase (90% of

cycle) G1 phase~ growth S phase~ synthesis of

DNA G2 phase~ preparation

for cell division2. Mitotic phase3. Mitosis~ nuclear

division4. Cytokinesis~

cytoplasm division INTERPHASE - It is thetime between divisions


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The Cell

Cycle G1

S

G2

Mitosis &

cytokinesis


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Cell Cycle

regulation

Growth factors

Density-dependent

inhibition Anchorage

(=tempat)dependence


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Stages of Mitosis


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Mitosis

1.

Prophase2. Prometaphase

3. Metaphase

4. Anaphase

5. Telophase


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Mitosis in Action

Blue showsDNA, green

shows spindle

fibers.


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Stages of mitosis


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Stages of mitosis


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PROPHASE, METAPHASE,ANAPHASE,TELOPHASE

1. Prophase: Chromosomes condense and become visible,

each Chromosome contains several cm of DNA

condensed into 5 10 micrometers. During the S Phase each chromosome has been

duplicated into a sister chromatid. (A chromotidis one of the two halves of duplicated

chromosomes)

S Phase = synthesis of DNA


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Prometaphase

Nuclear membranefragments

Spindle interactionwith chromosomes

Kinetochore develops


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Centrosomes at opposite poles Centromeres are aligned (=disejajarkan) Kinetochores of sister chromatids attached to

microtubules (spindle)

2. Metaphase:1. Chromosomes line up along the cell

equator.2. The cell itself condenses and the

chromosomes are more clearly visible thanduring any other phase of mitosis


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Paired centromeres separate; sister chromatidsliberated

Chromosomes move to opposite poles

Each pole now has a complete set ofchromosomes

3. Anaphase1. is defined as the sister chromatids begin to

separate2. By now each chromatid is an independent andfunctional chromosome

3. The chromosomes are pulled toward oppositepoles. Anaphase is complete when a complete

set of chromosomes reaches each pole.


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4. Telophase:

1. The final stage of mitosis, chromosomes

uncoil (= mengurai) into chomatin threads2. A nuclear envelope forms around each set of

chromosomes, nucleoli appear

Daughter nuclei form Nuclear envelopes arise Chromatin becomes less coiled (=

menggulung)

Two new nuclei complete mitosis


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Structure of a replicatedchromosome


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Counting chromosomes and chromatids

n = haploid number of chromosomes Example: the humans have 23 different

chromosomes (n=23).

Diploid cells have 2n chromosome #.

Human diploid cells, have 46 chromosomes(2n=46).

c = number of chromatids inunreplicated (G1) haploid state.


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Replication of achromosome during mitosis


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1.

Frequency of mitosis varies between species oreven with location within an organismskin cellversus nerve cells for example, but undersimilar conditions the length of the cell cycle isconstant for a particular type of cell.

2. The rate and frequency of mitosis in amulticelluar organism must be controlled

3. The cell requires a protein called maturationpromoting factor (MPF). Scientists are still

learning how MPF works and controls the cellmitosis.

CONTROLS ON DIVISION


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Read about the effects of Colchicine and

the condition of polypoidy When mitosis occurs each daughter cell

receives exactly the same number and

kind of chromosomes as the parent When a haploid cell undergoes mitosis,

two haploid cells are produced.


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These are Organisms

(living things)

mitosis krt baru

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