biodas cell division

8/2/2019 Biodas Cell Division

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Cell DivisionMitosis & Meiosis

Yoga Dwi Jatmiko, S.Si., M.App.Sc

Basic Biology for Food Tech. Faculty

2012


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Mitosis

Eukaryotes divide by a more complicated system called Mitosis This is because:

1. They have a nucleus which must be broken up and thenreformed

2.They have their DNA packaged in the form ofChromosomes

3. Chromosomes are composed of ChromatinMade of DNA Strands & Proteins

4. Also contain Nucleosomes containing Histones Proteinsthe DNA is wrapped around Name for the DNA/Proteincomplex is Chromatin

5. They usually have more than 1 chromosome (Humans have23 pairs)

6. They have numerous organelles to equally share


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Chromatin / Chromosomes


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All chromosomes are duplicated

Do they contain identical genes?

That means: two copies of each chromosome

What are the copies called?

Sister chromatids

Yes, but

What about meiosis?


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Some terminology

Double-chromatid chromosomes

Single-chromatid chromosomes

Chromatin

Homologous chromosomes

Chromatid

When do each of these occur?


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The Cell Cycle

Most of the cell's life is spent doingits regular function.Cells divide along a rough time framecalled its Cell Cycle.The Cell cycle consists of the

folowing steps:G1 (Gap 1) Phase - Cell performs itsnormal function (cells which do notdivide stay in this stage for theirentire life span)S (Synthesis) Phase - Here the cell

actively duplicates its DNA inpreparation for divisionG2 (Gap 2) Phase - Amount ofcytoplasm (including organelles)increases in preparation for division.Mitosis - Actual division occurs


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Interphase

Cell Replicates its DNA/Chromosomesin preparation of upcoming division

Animal Cell Plant cell


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Prophase

1.Chromosomes Shortenand become visible.

2. Centrioles move toopposite sides of thecell

3. Nuclear envelopedisappears

4. Spindle Fibers & AstralFibers both togetherare known as theSpindle Apparatusbegin to form

Animal Cell

Plant Cell


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Metaphase

Chromosomes line upalong center of cellcalled the

Metaphase Plate Chromosomes attach

to spindle fibers

Spindle & Astralfibers are nowclearly visible

Animal Cell

Plant Cell


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Anaphase

Centromeres breakup separatingchromosome copies

Chromosomes arepulled apart toopposite sides of cell

Spindle & Astralfibers begin tobreak down

Animal Cell

Plant Cell


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Telophase (cytokenesis)

Nuclear envelope formsaround both sets ofchromosomes

DNA uncoils

Spindle & Astral fiberscompletely disappear Cytokenesis happens with

most (but not all) cells Cytoplasm & organelles

move (mostly equally) toeither side of the cell.CellMembrane pinches toform 2 separate cells

AnimalCell

PlantCell


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Plant and Animal cells dividedifferently


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Centrioles

Chromatin

Interphase

Nuclearenvelope

Cytokinesis

Nuclearenvelopereforming

Telophase

Anaphase

Individualchromosomes

Metaphase

Centriole

Spindle

CentrioleChromosomes

(paired chromatids)

Prophase

Centromere

Spindleforming

Interphase

G1 - Cell grows

S - DNA duplicates

G2 - Cell prepares for division


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Centrioles

Chromatin

Interphase

Nuclearenvelope

Cytokinesis


Telophase

Anaphase


Metaphase

Centriole

Spindle


(paired chromatids)

Prophase

Centromere

Spindleforming

Mitosis - Prophase

1. DNA condenses to form chromosomes

2. Spindle forms


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Centrioles

Chromatin

Interphase

Nuclearenvelope

Cytokinesis


Telophase

Anaphase


Metaphase

Centriole

Spindle


(paired chromatids)

Prophase

Centromere

Spindleforming

Mitosis - Metaphase

Chromosomes line up along the middle of the cell


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Centrioles

Chromatin

Interphase

Nuclearenvelope

Cytokinesis


Telophase

Anaphase


Metaphase

Centriole

Spindle


(paired chromatids)

Prophase

Centromere

Spindleforming

Mitosis - Anaphase

Chromosomes separate and are pulled to

opposite sides of the cell


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Centrioles

Chromatin

Interphase

Nuclearenvelope

Cytokinesis


Telophase

Anaphase


Metaphase

Centriole

Spindle


(paired chromatids)

Prophase

Centromere

Spindleforming

Mitosis - Telophase

1. Nuclear envelope forms

2. Cell contents are separated as the cells begin to

pinch apart


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Centrioles

Chromatin

Interphase

Nuclearenvelope

Cytokinesis


Telophase

Anaphase


Metaphase

Centriole

Spindle


(paired chromatids)

Prophase

Centromere

Spindleforming

Cytokinesis

Cells pinch off to form two daughter cells each

genetically identical to the parent cell


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Putting it all together


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Mitosis Questions

1. What does diploid mean?

2. We have __ total chromosomes.

3. In the term 2n, what does n stand for inus?

4. Why does mitosis occur? Majorfunctions?

5. In what cells (general term) does mitosisoccur?


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Meiosis

A. Phases of Meiosis

1. Meiosis I2. Meiosis II

B. Comparing Mitosis and Meiosis

Go toSection:

M i i


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Meiosis

Chromosome replicate

2 Cell divisions occur(Meiosis I & MeiosisII)

4 daughter cells aremade all are (n):haploid

Homologous Chromsseparate in meiosis I

Meiosis II = Mitosis(chromatids separate)


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Meiosis

Gametes sex cells; egg and sperm Homologous Chromosomes - chromosomes in a cell that

pair during meiosis because they code for similargenes/features. For example, two chromosomes may

have genes encoding eye color, but one may code forbrown eyes (from mom), the other for blue (from dad). Diploid (2N) cells (somatic) that have two homologous

copies of each chromosome, usually one from themother and one from the father. (Humans = 46

chromosomes) Haploid (n) - the number of chromosomes in a gamete

of an individual. (Humans = 23 chromosomes)


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Interphase I Prophase I Metaphase I Anaphase I

Cells undergo a roundof DNA replication,

forming duplicateChromosomes.

Each chromosome pairswith its corresponding

homologous chromosometo form a tetrad.

Spindle fibers attach to thechromosomes.

The fibers pull thehomologous chromosomes

toward the opposite ends ofthe cell.

Go toSection:

Meiosis I


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homologous chromosometo form a tetrad. Crossingover occurs.




Go toSection:

Meiosis I


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Go toSection:

Crossing Over (Synapsis)

The chance that any two sex cells will be identical is 1 in 8,388,608!


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Crossing Over

During metaphase 1homologouschromosomes line-up

along the metaphaseplate

Areas of homologouschromosomes

connect at areascalled chiasmata


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Figure 8.18A

TetradChaisma

Centromere


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Crossing over contd.

Crossing Over of genesoccurs now Segments of homologous

chromosomes break and

reform at similarlocations.

Results in new geneticcombinations ofoffspring.

This is the mainadvantage of sexualreproduction


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Chromosome reduction

During anaphase 1,each homologouschromosome ispulled to opposite

sides of the cell.Unlike mitosis,THECENTROMERES

DO NOT BREAK.


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Go toSection:

Meiosis I


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Go toSection:

Meiosis I


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Meiosis I results in twohaploid (N) daughter cells,each with half the numberof chromosomes as theoriginal.

Prophase II Metaphase II Anaphase II Telophase IIThe chromosomes line upin a similar way to themetaphase stage of mitosis.

The sister chromatidsseparate and move towardopposite ends of the cell.

Meiosis II results in fourhaploid (N) daughter cells.

Go toSection:

Meiosis II


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Go toSection:

Meiosis II


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Go toSection:

Meiosis II


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Go toSection:

Meiosis II


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Go toSection:

Meiosis II


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Meiosis Summary

2. Meiosis 2a. There is no more DNA replication

b. The chromatids of each chromosome

separate and each daughter cell dividesc. At the end of Meiosis 2, there are 4daughter cells from each parent cell. Eachdaughter cell has half the number of

chromosomes as the parent cell


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1. The cells produced in meiosis are_____ (haploid or diploid?)

2. Sex cells are called ________.

_____ are produced by males, ____by females.

3. Whats crossing over and why is itimportant?

Meiosis Questions


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4. In what meiotic stage does crossingover occur?

5. Why are sex cells n, not 2n?

6. If a species diploid number is 50,what is n?

Meiosis Questions

Diff B t Mit i d M i i


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Differences Between Mitosis and MeiosisMitosis Meiosis

Interphase

chromosomesduplicate

Interphase I

chromosomesduplicate

Prophase homologous

chromosomes do not cross over

Prophase I homologous

chromosomes do cross over

Metaphase chromosomes all

lined up in a single row

Metaphase I chromosomes all

lined up in a double row

Anaphase chromatids

separate

Anaphase I chromatids do not

separate

Telophase homologous

chromosomes not separated

Telophase I homologous

chromosomes separate

Each daughter cell has the same

number of chromosomes as the

original cell (diploid, 2n)

PMAT repeats.

Each daughter cell has half the

number of chromosomes as the

original cell (haploid, n) and is

genetically unique


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Figure 8.15

MITOSIS MEIOSIS

PARENT CELL(before chromosome replication)

Site ofcrossing over

MEIOSIS I

PROPHASE ITetrad formed

by synapsis ofhomologouschromosomes

PROPHASE

Duplicatedchromosome(two sister chromatids)

METAPHASE

Chromosomereplication

Chromosomereplication

2n= 4

ANAPHASETELOPHASE

Chromosomesalign at themetaphase plate

Tetradsalign at themetaphase plate

METAPHASE I

ANAPHASE ITELOPHASE I

Sister chromatidsseparate duringanaphase

Homologouschromosomesseparateduringanaphase I;sisterchromatids

remain together

No furtherchromosomalreplication; sisterchromatidsseparate duringanaphase II

2n 2n

Daughter cellsof mitosis

Daughter cells of meiosis II

MEIOSIS II

Daughter

cells ofmeiosis I

Haploidn= 2

n n n n


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Bacteria andBinary Fission


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Thank you

biodas cell division

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