Cell Reproduction

Cell ReproductionCell Reproduction

ProkaryotesBacteria

EukaryotesPlants &

animals

ProkaryotesProkaryotes

Lack a nucleus Have a single chromosomeReproduce asexually by

binary fission Include bacteria

Asexual Reproduction contdAsexual Reproduction contd..

Binary fission– happens in bacteria, amoeba, some

algae– one parent cell splits into 2 identical

daughter cellsBudding

– happens in yeast, hydra, corals– parent produces a bud– bud gets detached and develops into

offspring which is identical to parent

Steps in Binary FissionSteps in Binary Fission

Used by bacteria Cells increase their

cell mass slightly DNA & cell

components are replicated

Each cell divides into 2 daughter cells

Binary Fission of Bacterial Binary Fission of Bacterial CellCell

BuddingBudding

EukaryotesEukaryotes

Contain a nucleus & membrane bound organelles

Asexually reproduce cells by mitosis

Also reproduce sexually

Sexual Reproduction in AnimalsSexual Reproduction in Animals involves specialized sex cells called gametes (haploid

Cells) the union of a male and female gamete results in the

formation of a zygote that develops into a new individual

Cell CycleCell Cycle

Stages in growth & division

G0 Resting Phase

G1 Phase S Phase G2 Phase M Phase Cytokinesis

G0 PhaseG0 Phase

After Cell DivisionCell At RestFrom here some cells will remain in the G0 Phase and others will go into G1.

G1 PhaseG1 Phase

First growth stageCell increases in sizeCell prepares to copy its DNA

Synthesis PhaseSynthesis Phase

Copying of all of DNA’s instructions

Chromosomes duplicated

G2 PhaseG2 Phase

Time between DNA synthesis & mitosis

Cell continues growingNeeded proteins produced

Mitosis PhaseMitosis Phase

Cell growth & protein production stop

Cell’s energy used to make 2 daughter cells (Diploid Cells)

Called mitosis or karyokinesis (nuclear division)

Life Cycle of a CellLife Cycle of a Cell

Mitosis is a cycle with no beginning or end.

Interphase – Resting StageInterphase – Resting Stage

Cells carrying on normal activities

Chromosomes aren’t visibleCell metabolism is occurringOccurs before mitosis

InterphaseInterphase

Stages of MitosisStages of Mitosis

ProphaseMetaphaseAnaphaseTelophase

Cells Undergoing MitosisCells Undergoing Mitosis

Steps in ProphaseSteps in Prophase

DNA coils tightly & becomes visible as chromosomes

Nuclear membrane disappears Nucleolus disappears Centrioles migrate to poles Spindle begins to form

ProphaseProphase

Eukaryotic ChromosomeEukaryotic Chromosome

Human ChromosomesHuman Chromosomes

Steps in MetaphaseSteps in Metaphase

Spindle fibers from centrioles attach to each chromosome

Cell preparing to separate its chromosomes

Cell aligns its chromosomes in the middle of the cell

MetaphaseMetaphase

Steps in AnaphaseSteps in Anaphase

Cell chromosomes are separated

Spindle fibers shorten so chromosomes pulled to ends of cell

Mitotic SpindleMitotic Spindle

AnaphaseAnaphase

Steps in TelophaseSteps in Telophase

Separation of chromosomes completed

Cell Plate forms (plants)Cleavage furrow

forms(animals)Nucleus & nucleolus reformChromosomes uncoil

TelophaseTelophase

       Plant             Animal

CytokinesisCytokinesis

Occurs after chromosomes separate

Forms two, identical daughter cells

CytokinesisCytokinesis

Cell Plate Forming in Plant Cells

Cell that do not go through Cell that do not go through MitosisMitosis

Muscle Cell-Why? Fused fibers preventing cell division

Some Neuron Cells –Why? Have lost there centrioles and can no longer reproduce.

Blood Cells-Why? Mature and No longer have a nucleus

Sex Cells: They go through meiosis. Most of the cells never leave the G0 phase.

CanceCancerr Cancer is a disease of uncontrolled cell division. It

starts with a single cell that loses its control mechanisms due to a genetic mutation. That cell starts dividing without limit, and eventually kills the host.

Normal cells are controlled by several factors. – Normal cells stay in the G1 stage of the cell cycle

until they are given a specific signal to enter the S phase, in which the DNA replicates and the cell prepares for division. Cancer cells enter the S phase without waiting for a signal.

– Normal cells are mortal. This means that they can divide about 50 times and then they lose the ability to divide, and eventually die. This “clock” gets re-set during the formation of the gametes. Cancer cells escape this process of mortality: they are immortal and can divide endlessly.

THE ENDTHE END