SIKLUS SEL BUD.pptx

SIKLUS SEL

Figure 12.1

Kontinuitas kehidupanDidasarkan atas reproduksi sel atau pembelahan sel

100 µm

(a) Reproduction. An amoeba, a single-celled eukaryote, is dividing into two cells. Each new cell will be an individual organism (LM).

• Organisme multiseluler tergantung pada pembelahan sel untuk:

– Perkembangan (dari sel yang terfertilisasi)– Pertumbuhan– Repair

20 µm200 µm

(b) Growth and development. This micrograph shows a sand dollar embryo shortly after the fertilized egg divided, forming two cells (LM).

(c) Tissue renewal. These dividing bone marrow cells (arrow) will give rise to new blood cells (LM).

Figure 12.2 B, C

Semua organisme kompleks berasal dari a single fertilized egg.

Melalui pembelahan sel, jumlah sel meningkat

Sel kemudian terspesialisasi dan berubah menjadi fungsinya masing2

Tipe pembelahan sel

• Mitosis: – Growth, development & repair– Asexual reproduction (yields identical cells)– Occurs in somatic (body) cells

• Meiosis:– Sexual reproduction (yields different cells)– Occurs in specific reproductive cells

Phases of Mitosis

1. Prophase2. Prometaphase3. Metaphase4. Anaphase5. Telophase

• Pembelahan sel menghasilkan sel anak yang secara genetik identik

• Sel harus menduplikasikan material genetiknya– Before they divide, ensuring that each daughter cell

receives an exact copy of the genetic material, DNA

Distribution of Chromosomes During Cell Division

• Pada persiapan cell division, DNA bereplikasi dan kromosom memadat

• Tiap chromosome yang terduplikasi memiliki dua sister chromatids, yang berpisah selama cell division

• Sentromer merupakan daerah ceking dari chromosome yang terduplikasi, diaman dua chromatids terikat dengan dekat

Figure 12.1

prophase

1X

metahase

Anaphase

Telophase

Cytokinesis

Cell division results in genetically identical daughter cells

• Sel menduplikasikan material genetik sebelum membelah, utk memastikan bahwa tiap sel anak menerima copy DNA dengan tepat

• A cell’s endowment of DNA (its genetic information) is called its genome

• Molekul DNA dalam sel ter-pack menjadi kromosom

• Setiap spesies eukariot memiliki sejumlah tertentu kromosom pada nukleus

• Sel somatik (nonreproductive) memiliki 2 set kromosom

• Gamet (reproductive cells: sperm and eggs) memiliki jumlah kromosom setengah jumlah kromosom sel somatik

• Kromosom eukaryotik terdiri dari kromatin, sebuah komplex DNA dan protein yang memampat selama pembelahan sel

0.5 µm

Chromosomeduplication(including DNA synthesis)

Centromere

Separation of sister chromatids

Sisterchromatids

Centromeres Sister chromatids

A eukaryotic cell has multiplechromosomes, one of which is

represented here. Before duplication, each chromosome

has a single DNA molecule.

Once duplicated, a chromosomeconsists of two sister chromatids

connected at the centromere. Eachchromatid contains a copy of the

DNA molecule.

Mechanical processes separate the sister chromatids into two chromosomes and distribute

them to two daughter cells.

Figure 12.4

• Pembelahan sel pada eukariot terdiri dari:– Mitosis, the division of the nucleus– Cytokinesis, the division of the cytoplasm

• Gamet diproduksi dalam pembelahan sel yang disebut meiosis

• Meiosis menghasilkan sel anak yang tidak identik dengan induk yaitu hanya memiliki 1 set kromosom

Pada pembelahan sel, fase mitosis bergantian dengan interfase

• Pada tahun 1882, ahli anatomi Jerman Walther Flemming mengembangkan pewarna untuk mengamati kromosom selama mitosis dan sitokinesis

• Bagi Flemming, terlihat sel tumbuh membesar• Sekarang dapat diketahui banyak peristiwa kritis terjadi

selama tahapan siklus sel

Fase-fase dalam siklus sel• Siklus sel terdiri dari

– Fase mitosis– Interphase

• Interphase– G1 phase– S phase– G2 phase

• The mitotic phase– mitosis – cytokinesis

Phases of the Cell Cycle

• Siklus sel terdiri dari– Mitotic (M) phase (mitosis and cytokinesis)– Interphase (cell growth and copying of

chromosomes in preparation for cell division)• Interphase (terdiri dari sekitar 90% dari siklus

sel) yang dapat dibagi dalam sub fase:– G1 phase (“first gap”)– S phase (“synthesis”)– G2 phase (“second gap”)

• Mitosis terdiri dari 5 phases– Prophase– Prometaphase

G2 OF INTERPHASE PROPHASE PROMETAPHASE

Centrosomes(with centriole pairs) Chromatin

(duplicated)

Early mitoticspindle

AsterCentromere

Fragmentsof nuclearenvelope

Kinetochore

Nucleolus Nuclearenvelope

Plasmamembrane

Chromosome, consistingof two sister chromatids

Kinetochore microtubule Figure 12.6

Nonkinetochoremicrotubules

– Metaphase– Anaphase– Telophase

Centrosome at one spindle pole

Daughter chromosomes

METAPHASE ANAPHASE TELOPHASE AND CYTOKINESIS

Spindle

Metaphaseplate Nucleolus

forming

Cleavagefurrow

Nuclear envelopeforming

Figure 12.6

• The mitotic spindle– mikrotubul yang mengontrol pergerakan kromosom

selama mitosis

• Spindle muncul dari sentromer– spindle microtubules – asters

• Perakitan spindle microtubules dimulai dari sentrosom - microtubule organizing center

• Sentrosom bereplikasi membentuk dua sentrosom yang bermigrasi ke kutub yang berlawanan, dan spindle microtubules tumbuh dari sentrosom

• Aster (a radial array of short microtubules) muncul dari tiap sentrosom

The Spindle

Spindle memiliki struktur seperti web terbuat dari microtubule . Sangat penting pada mitosis karena mengatur kromosom untuk berada pada posisi yang benar

Mitotic center

MicrotubuleA cell at metaphase a spindle

• Some spindle microtubules– Berikatan dengan kinetochores chromosomes

CentrosomeAster

Sisterchromatids

MetaphasePlate

Kinetochores

Overlappingnonkinetochoremicrotubules

Kinetochores microtubules

Centrosome

ChromosomesMicrotubules 0.5 µm

1 µm

Figure 12.7

Chromosomes attached to spindle during nuclear division

Two kinds of microtubules

• Kinetochore microtubules : berikatan dengan kinetochores chromosomes dan menggerakkan kromosom ke daerah metafase

• Nonkinetochores: overlap satu sama lain tetapi tidak berikatan dengan chromosome

1 µm

• Pada anafase, sister chromatid berpisah– Dan bergerak sepanjang kinetochore microtubules

menuju arah berlawanan ujung sel

Spindlepole

Kinetochore

Figure 12.8

Initiation ofAnaphase

• Nonkinetechore microtubules from opposite poles– Overlap and push against each

other, elongating the cell• In telophase

– Genetically identical daughter nuclei form at opposite ends of the cell

• The microtubules shorten by depolymerizing at their kinetochore ends

CYTOKINESIS

Division of the cytoplasm

Mitosis is the splitting of the nucleus.

Cytokinesis is the splitting of cytoplasm

It usually begins during ANAPHASE

• Pada sel hewan– Cytokinesis terjadi oleh proses yang disebut

cleavage, membentuk sebuah a cleavage furrow

Cleavage furrow

Contractile ring of microfilaments Daughter cells

100 µm

(a) Cleavage of an animal cell (SEM)

• Pada sel tumbuhan, selama cytokinesis– Terbentuk plat sel (cell plate)

Daughter cells

1 µmVesiclesforming cell plate

Wall of patent cell Cell plate New cell wall

(b) Cell plate formation in a plant cell (SEM)Figure 12.9 B

• Mitosis in a plant cell

1 Prophase. The chromatinis condensing. The nucleolus is beginning to disappear.Although not yet visible in the micrograph, the mitotic spindle is staring to from.

Prometaphase.We now see discretechromosomes; each consists of two identical sister chromatids. Laterin prometaphase, the nuclear envelop will fragment.

Metaphase. The spindle is complete,and the chromosomes,attached to microtubulesat their kinetochores, are all at the metaphase plate.

Anaphase. Thechromatids of each chromosome have separated, and the daughter chromosomesare moving to the ends of cell as their kinetochoremicrotubles shorten.

Telophase. Daughternuclei are forming. Meanwhile, cytokinesishas started: The cellplate, which will divided the cytoplasm in two, is growing toward the perimeter of the parent cell.

2 3 4 5

NucleusNucleolus

ChromosomeChromatinecondensing

Figure 12.10

Purpose of Interphase – to duplicate cell contents; 90% of the cell’s growth cycle

Purpose of Mitosis – to divide the genetic material into exact two halves

Purpose of Cytokinesis – to divide all other contents (except nucleus) into two cells

In binary fission– The bacterial chromosome replicates– The two daughter chromosomes actively move apart

Prokaryotes (bacteria and archaea) reproduce by a type of cell division called binary fission

LE 12-11_1

Origin ofreplication

Cell wall

Plasmamembrane

Bacterialchromosome

E. coli cell

Two copiesof origin

Chromosome replication begins. Soon thereafter, one copy of the origin moves rapidly toward the other end of the cell.

LE 12-11_2

Origin ofreplication

Cell wall

Plasmamembrane

Bacterialchromosome

E. coli cell

Two copiesof origin

Chromosome replication begins. Soon thereafter, one copy of the origin moves rapidly toward the other end of the cell.

Replication continues. One copy of the origin is now at each end of the cell.

Origin Origin

LE 12-11_3Origin ofreplication

Cell wall

Plasmamembrane

Bacterialchromosome

E. coli cell

Two copiesof origin

Chromosome replication begins. Soon thereafter, one copy of the origin moves rapidly toward the other end of the cell.

Replication continues. One copy of the origin is now at each end of the cell.

Origin Origin

Replication finishes. The plasma membrane grows inward, and new cell wall is deposited.

Two daughtercells result.

A comparison of mitosis and meiosis

A comparison of mitosis and meiosis: summary