Antum Cell Reproduction_rombel 1 Pend Bio 2010

8/3/2019 Antum Cell Reproduction_rombel 1 Pend Bio 2010

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Cell Reproduction

Also called

Cell Division

By:

Kharis Subkhan(4401410010)

&

Armya Aisyah Kinanti(4401410089)



• Pollen

– Develops from microspores within

the sporangia of anthers

3 A pollen grain becomes a

mature male gametophyte

when its generative nucleus

divides and forms two sperm.

This usually occurs after a

pollen grain lands on the stigma

of a carpel and the pollen

tube begins to grow. (See

Figure 38.2b.)

Development of a male gametophyte

(pollen grain)

(a)

2 Each microsporo-

cyte divides by

meiosis to produce

four haploid

microspores,

each of which

develops into

a pollen grain.

Pollen sac

(microsporangium)

Micro-

sporocyte

Micro-

spores (4)

Each of 4

microspores

Generative

cell (willform 2

sperm)

MaleGametophyte

(pollen grain)

Nucleus

of tube cell

Each one of the

microsporangia

contains diploid

microsporocytes

(microsporemother cells).

1

75 m

20 m

Ragweed

pollen

grain

Figure 38.4a

MEIOSIS

MITOSIS

KEY

to labels

Haploid (2n)

Diploid (2n)



Cell Division

• Cell division consists of two phases:

• 1. the division of the nucleus, and

•

2. the division of the cytoplasm (cytokinesis)



2 Kinds of Nuclear Division

• 1. Mitosis – mitosis divides the nucleus so that

both resulting new cells (daughter cells) are

genetically identical…Same amount of DNA

• 2. Meiosis – meiosis produces daughter cells

that contain half the genetic information… half

the amount of DNA.



Before Division Begins

• Before a cell can successfully divide, the DNA

must be packaged so it does not get damaged.

The “stringy” form of DNA (chromatin) is

coiled into structures called “chromosomes”.



Sister Chromatids

Each Chromosome is

made up of twoidentical halves called

“sister chromatids”

joined at the

centromere.

Each Chromatid is asingle, coiled DNA

molecule.

The point where two

sister chromatids areconnected.



Organizing Chromatin into a Chromosome.



Chromosomes

Chromosomes



The Life Cycle of a cell is called

The “Cell Cycle”

The Cell Cycle consists of 5 Phases

1.Interphase (part of the cell cycle, but not part of mitosis)

2.Prophase3.Metaphase

4.Anaphase

5.Telophase

These 4 phases are known

collectively as “Mitosis”



Interphase

90% of cell’s life is spent in interphase

During Interphase the cell grows, duplicates its

chromosomes and performs its normal job.

Interphase has 3 stages

The Events of Interphase

G1 stage - first gap - Cell grows and carries out regular biochemical functions.

S stage – synthesis - DNA is replicated or synthesized.

G2 stage - second gap - Cell completes preparations for division…..a cell can

complete S, but fail to enter G2.





Plant Cells



Mitosis (the splitting of the nucleus)

prophasemetaphase

anaphase

telophase



Mitosis

• A cell that has grown in

size and is about to

divide is called a

“Mother Cell”. • As a result of Mitosis

and cytokinesis the

Mother cell splits into

two genetically identical“Daughter Cells”.

Mother

Cell



The Events of Prophase

• Nucleoli disappear.

• Chromatin condenses into thechromosomes.

• Nuclear Envelope dissolves… thenucleus comes apart

•

Centrioles (MTOC’s) separateand move to opposite ends of the cell.

• Microtubules from each MTOCconnect to a specialized region of

the centromere called thekinetochore. This moves the

chromosomes back and forth.

• Mitotic spindle begins to form.



Plant Cells



Events of Metaphase

• Chromosomes line up at theequator of the cell…. called the

“metaphase plane”.

• Centrioles arrive at oppositeends of the cell.

• Spindle apparatus fullydeveloped.

• Metaphase ends when themicrotubules pull each

chromosome apart into twochromatids. Once separated

from its sister chromatid, eachchromatid is now called achromosome. To count the

number of chromosomes, atany time, count the number of

centromeres.metaphase plane

centriole

centriole



Plant Cells



Events of Anaphase

• Anaphase begins when thechromosomes separate.

• Microtubules shorten astubulin units uncouple, the

chromosomes are pulledaway from each other toward

opposite ends of the cell.

• Cell elongates; poles moveslightly further apart.

• Anaphase ends when thechromosomes reach theirrespective ends of the cell.

Chromosomes



Plant Cells



Events of Telophase

• Chromosomes uncoil back to chromatin.

• Nuclear envelope reforms. The nucleus

reforms in each newly formed cell.

• Nucleoli reappear.

• Spindle fibers disappear.

•

Simultaneously Cytokinesis usually starts.



Plant Cells



Plant Cell Cytokinesis

• Cell plate develops from Golgi vesicles.

• New cell wall developed around the cell plate.

p



Cell Plate



Cytokinesis



Plant Cell - Mitosis



Meiosis reduces the

number of

chromosome sets fromdiploid to haploid

Takes place in two

sets of divisions,

meiosis I and

meiosis II

Interphase

Homologous pair

of chromosomes

in diploid parent cell

Chromosomes

replicate

Homologous pair of replicated chromosomes

Sister

chromatids Diploid cell with

replicated

chromosomes

1

2

Homologous

chromosomes

separate

Haploid cells with

replicated chromosomes

Sister chromatids

separate

Haploid cells with unreplicated chromosomes

Meiosis I

Meiosis II



Centrosomes

(with centriole pairs)Sister

chromatids

Chiasmata

Spindle

Tetrad

Nuclear

envelopeChromatin

Centromere

(with kinetochore)

Microtubule

attached to

kinetochoreTertads line up

Metaphase

plate

Homologous

chromosomes

separate

Sister chromatids

remain attached

Pairs of homologous

chromosomes split upChromosomes duplicate

INTERPHASE MEIOSIS I: Separates homologous chromosomes

PROPHASE I METAPHASE I ANAPHASE I

TELOPHASE I AND

CYTOKINESISPROPHASE II METAPHASE II ANAPHASE II

TELOPHASE II AND

CYTOKINESIS

MEIOSIS II: Separates sister chromatids

Cleavage

furrow Sister chromatids

separate

Haploid daughter cells

forming

During another round of cell division, the sister chromatids finally separate;four haploid daughter cells result, containing single chromosomes

Two haploid cells

form; chromosomes

are still double



INTERPHASE IThe phase when cells

grow and develop. Isto hold a preparatorystage of cell division.In this phase of DNA

duplication eventsfrom one copy intotwo copies. End of phase produced twocopies of DNA andready to turn intochromosomes

PROPHASE I



PROPHASE I

1. Leptoten

This phase is characterized by chromatin thread turned into a chromosome.

2. ZigotenThis phase is characterized by homologous chromosomes close together and in pairs to form synapses, or bivalent.

3. pachytene

In this phase there duplication or replication of chromosomes, the centromere into two chromatids that are still

together or berlekatan and not divide, so-called tetrad. In this phase can occur between the chromosome arm chiasma.

Chiasma is the site of crossovers.

4. Diploten

Homologous chromosomes move away from each other.

5. Diakinesis

This phase is marked by the emergence of yarn spindles that came out between the two centrioles, which has been at

opposite poles. In this phase, the nucleolus and nucleus membrane disappears, and tetrad began moving toward the

equator site.



Still PROPHASE I…

The chromosomes are

completely condensed.

In meiosis (unlike

mitosis), the

homologous

chromosomes pair with

one another



METAPHASE I

This phase is characterizedby:1. Homologous

chromosomes (tetrads)arrange themselves in thefield of the equator /division

2. Each chromosome bindsto the spindle at thecentromere threads



ANAPHASE I

The chromosomes

move to opposite

ends of the cell.



TELOPHASE I & CYTOKINESIS

The cell begins todivide into two

daughter cells.



PROPHASE II

The cell has divided into

two daughter cells.



METAPHASE II

As in Meiosis I, the

chromosomes line up

on the spindle fibers.



ANAPHASE II

The two cells each

begin to divide. As in

Meiosis I, the

chromosomes move toopposite ends of each

cell.



TELOPHASE II & CYTOKINESIS

With the formation of

four cells, meiosis is

over. Each of these

prospective germ cellscarries half the number

of chromosomes of

somatic cells.



MITOSIS MEIOSIS

Prophase

Duplicated chromosome

(two sister chromatids)

Chromosome

replication

Chromosome

replication

Parent cell

(before chromosome replication)

Chiasma (site of

crossing over)MEIOSIS I

Prophase I

Tetrad formed by

synapsis of homologous

chromosomes

Metaphase

Chromosomespositioned at the

metaphase plate

Tetradspositioned at the

metaphase plate

Metaphase I

Anaphase I

Telophase I

Haploidn = 3

MEIOSIS II

Daughter

cells of

meiosis I

Homologues

separate

during

anaphase I;

sisterchromatids

remain together

Daughter cells of meiosis II

n n n n

Sister chromatids separate during anaphase II

Anaphase

Telophase

Sister chromatids

separate during

anaphase

2n 2n

Daughter cells

of mitosis

2n = 6

• A comparison of mitosis and meiosis

Antum Cell Reproduction_rombel 1 Pend Bio 2010

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