Cell Division-Proliferation Cell Division: An overview.

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Cell Division- Cell Division- Proliferation Proliferation Cell Division: An Cell Division: An overview overview

Transcript of Cell Division-Proliferation Cell Division: An overview.

Page 1: Cell Division-Proliferation Cell Division: An overview.

Cell Division-ProliferationCell Division-ProliferationCell Division: An overviewCell Division: An overview

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Two fundamental characteristics of life Two fundamental characteristics of life are:are:

Ability to growAbility to grow Ability to reproduceAbility to reproduce Both of these characteristics depend on Both of these characteristics depend on

the process of the process of cell divisioncell division.. Cell division is the process by which a Cell division is the process by which a

single cell generates new daughter cells.single cell generates new daughter cells.

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Types of reproductionTypes of reproduction

Asexual Reproduction-A form of Asexual Reproduction-A form of duplication that requires only one parent duplication that requires only one parent and results in two organisms that are and results in two organisms that are genetically identical to the parent.genetically identical to the parent.

Sexual Reproduction-The process of Sexual Reproduction-The process of reproduction involving the union of reproduction involving the union of gametes from two different parents.gametes from two different parents.

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Asexual Reproduction:Asexual Reproduction:

For single-celled organisms, binary fission For single-celled organisms, binary fission and mitosis are methods of asexual and mitosis are methods of asexual reproduction.reproduction.

Prokaryotes typically undergo binary Prokaryotes typically undergo binary fission whereas single-celled and fission whereas single-celled and multicellular eukaryotes undergo mitosis.multicellular eukaryotes undergo mitosis.

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Binary Fission:Binary Fission:

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Mitosis:Mitosis:

Mitosis produces new cells in multicellular Mitosis produces new cells in multicellular organisms that-organisms that-

Cause growth by increasing the number of Cause growth by increasing the number of cellscells

Replace lost cellsReplace lost cells Repair injuriesRepair injuries

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Sexual Reproduction:Sexual Reproduction:

As sexual reproduction requires two parents, As sexual reproduction requires two parents, this process results in genetically unique this process results in genetically unique individuals.individuals.

Meiosis is the process that produces the Meiosis is the process that produces the cells needed for sexual reproduction .cells needed for sexual reproduction .

Meiosis is different from mitosis.Meiosis is different from mitosis.In meiosis reproductive cells receive half of In meiosis reproductive cells receive half of

the parent cell’s genetic information.the parent cell’s genetic information.

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The Cell Cycle and MitosisThe Cell Cycle and Mitosis

The cell cycle consists of all the stages of The cell cycle consists of all the stages of growth and division for a eukaryotic cell.growth and division for a eukaryotic cell.

All eukaryotic cells go through the same basic All eukaryotic cells go through the same basic life cycle, but different cells vary in the amount of life cycle, but different cells vary in the amount of time they spend in various stages.time they spend in various stages.

The cell’s life cycle is a continuous process The cell’s life cycle is a continuous process without a beginning or an end. As cells complete without a beginning or an end. As cells complete one cycle , they begin the next.one cycle , they begin the next.

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Mitosis:StagesMitosis:Stages

InterphaseInterphase ProphaseProphase MetaphaseMetaphase AnaphaseAnaphase TelophaseTelophase CytokinesisCytokinesis

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InterphaseInterphase

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11stst Phase-Interphase Phase-Interphase

During this stage the cell engages in During this stage the cell engages in normal metabolic activities and prepares normal metabolic activities and prepares for the next cell division.for the next cell division.

Most cell spend greater part of their life in Most cell spend greater part of their life in the interphase stage.the interphase stage.

Interphase contains three phases-G1, S Interphase contains three phases-G1, S and G2.and G2.

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The G1 stage of InterphaseThe G1 stage of Interphase

During this phase the cell gathers nutrients and During this phase the cell gathers nutrients and other resources from its environment.other resources from its environment.

This allows the cell to grow in volume and to This allows the cell to grow in volume and to carry out its usual metabolic roles, such as carry out its usual metabolic roles, such as producing tRNA, mRNA, ribosomes , enzymes producing tRNA, mRNA, ribosomes , enzymes and other cell components.and other cell components.

G1 stage is often known as G0 stage in a cell G1 stage is often known as G0 stage in a cell when a cell remains in G1 stage for a long time when a cell remains in G1 stage for a long time and the cell is not moving forward through cell and the cell is not moving forward through cell cycle.cycle.

Cell divides in G1 and moves towards S phase.Cell divides in G1 and moves towards S phase.

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G1 G1 and and G0 G0 phasephase

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The S stage of InterphaseThe S stage of Interphase

During this stage DNA synthesis (replication) During this stage DNA synthesis (replication) takes place.takes place.

Two copies of the genetic material are formed in Two copies of the genetic material are formed in the chromosomes.the chromosomes.

DNA is found as a component of chromosomes.DNA is found as a component of chromosomes. The structure of a chromosome consists of DNA The structure of a chromosome consists of DNA

wrapped around histone proteins to form wrapped around histone proteins to form chromatin.chromatin.

As a cell gets ready to divide, the chromatin As a cell gets ready to divide, the chromatin coils and become visible as Chromosome.coils and become visible as Chromosome.

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Chromosome appears as Chromosome appears as two thread like parts lying two thread like parts lying side by side known as side by side known as chromatid.chromatid.

A chromatid is one of the A chromatid is one of the two parallel parts of a two parallel parts of a chromosome.chromosome.

Each chromatid contains Each chromatid contains one DNA.one DNA.

Sister chromatids are the Sister chromatids are the 2 chromatids of a 2 chromatids of a chromosome attached by chromosome attached by centromerecentromere

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mm

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The G2 stage of InterphaseThe G2 stage of Interphase

Final stage of interphase is G2.Final stage of interphase is G2. During this stage final preparations are made for During this stage final preparations are made for

mitosis.mitosis. The cell makes the cellular components it will The cell makes the cellular components it will

need to divide successfully.need to divide successfully. At this stage the nuclear membrane is intact.At this stage the nuclear membrane is intact. The chromatin is replicated but individual The chromatin is replicated but individual

chromosomes are not yet visible.chromosomes are not yet visible. Nucleolus , the site of ribosome manufacture is Nucleolus , the site of ribosome manufacture is

seen during this stage.seen during this stage.

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Summary of InterphaseSummary of Interphase I. Gap 1 (G1)I. Gap 1 (G1) This stage is characterized by the rapid growth and development of This stage is characterized by the rapid growth and development of

cell after nuclear division. The cell will grow into its original size. cell after nuclear division. The cell will grow into its original size.

II. Synthesis (S stage)II. Synthesis (S stage) The stage when cell actively duplicate its genetic information in The stage when cell actively duplicate its genetic information in

preparation for the next cell division. preparation for the next cell division.

III. Gap 2 (G2)III. Gap 2 (G2) The stage in which cells are actively synthesize energy, organelles The stage in which cells are actively synthesize energy, organelles

and grow to prepare for cell division. and grow to prepare for cell division.

Characteristics of cells during interphase Characteristics of cells during interphase Nucleus and nucleolus are visible. Nucleus and nucleolus are visible. Genetic information is in the form of loosely coil chromatin instead of Genetic information is in the form of loosely coil chromatin instead of

chromosomeschromosomes

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Let’s revise…………..Let’s revise…………..

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Concept ReviewConcept Review

What is a cell cycle?What is a cell cycle? What happens to chromosomes during What happens to chromosomes during

interphase?interphase? What are the types of cellular What are the types of cellular

reproduction?reproduction? What is the purpose of binary fission and What is the purpose of binary fission and

mitosis in comparison to meiosis?mitosis in comparison to meiosis? What is the role of interphase in cell cycle?What is the role of interphase in cell cycle?