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Cell ReproductionCell Reproduction
Cell division in necessary to form Cell division in necessary to form multi-cellular organisms.multi-cellular organisms.
Asexual Reproduction:Asexual Reproduction: Production of offspring from one parent cell.Production of offspring from one parent cell.
Sexual Reproduction:Sexual Reproduction: Formation of offspring from the union of two Formation of offspring from the union of two
gamete cells . gamete cells .
Asexual ReproductionAsexual Reproduction
Steps:Steps: Chromosomes duplicate (called Chromosomes duplicate (called
replication)replication) Both attach to a site located in the cellBoth attach to a site located in the cell They are forced apart.They are forced apart.
Cell membrane constricts them till they Cell membrane constricts them till they separate.separate.
ChromosomesChromosomes
Chromatids: Chromatids: Long strands of DNA.Long strands of DNA.
Chromosomes:Chromosomes: Made of two sister chromatids.Made of two sister chromatids.
Held together by a centromereHeld together by a centromere
Diploid (2n) CellsDiploid (2n) Cells
A cell with two of each kind of A cell with two of each kind of chromosomes are called chromosomes are called Diploid CellsDiploid Cells..
Haploid (n) CellsHaploid (n) Cells
A cell with one kind of each chromosome A cell with one kind of each chromosome is called a is called a HaploidHaploid cell. cell.
MitosisMitosis
Cells undergo mitosis as they reach their Cells undergo mitosis as they reach their maximum cell size. maximum cell size.
There are four steps in mitosis:There are four steps in mitosis: ProphaseProphase MetaphaseMetaphase AnaphaseAnaphase TelophaseTelophase
Mitosis:Mitosis:
Stage 1 – Prophase.Stage 1 – Prophase. Chromatids coil up into visible
chromosomes. Nucleus Disappears Centrioles migrate to the polar ends of
the cell Spindle Fibers begin to form.
Mitosis:Mitosis:
Stage 2 – MetaphaseStage 2 – Metaphase Chromosomes become attached to the
spindle fibers by their centromeres. They are lined up across the center of
the cell.
Mitosis:Mitosis:
Stage 3 – AnaphaseStage 3 – Anaphase Sister chromatids begin to separate Chromatids are pulled apart, and
separate from each other.
Mitosis:Mitosis:
Stage 4 – TelophaseStage 4 – Telophase New cells prepare for their new
existence. Chromosomes uncoil and direct
metabolic activity Spindle Fibers break down Nucleolus reappears Double membrane forms between them
MitosisMitosis
CytokinesisCytokinesis AnimalsAnimals – Plasma Membrane pinches – Plasma Membrane pinches
in along the equator of the cell.in along the equator of the cell.
MitosisMitosis
CytokinesisCytokinesis Plants Plants - Cell Plate is laid across the - Cell Plate is laid across the
equator.equator. Cell walls form around the plateCell walls form around the plate
Results of MitosisResults of Mitosis
As a result, As a result, Each daughter cell receives and exact Each daughter cell receives and exact
copy of the chromosomes present in the copy of the chromosomes present in the parent cell. parent cell.
They copy their chromosomes during They copy their chromosomes during Interphase.Interphase.
They become a diploid cell 2nThey become a diploid cell 2n The process can then start over.The process can then start over.
Results of MitosisResults of Mitosis
Process that guarantees that genetic Process that guarantees that genetic continuity.continuity.
The two new cells formed will carry out The two new cells formed will carry out the same functions of the parent cell. the same functions of the parent cell.
They will grow and divide just like the They will grow and divide just like the parent cells.parent cells.
Results of MitosisResults of Mitosis
As a result of cell division we have As a result of cell division we have groups of cells working together, until groups of cells working together, until they create and organism, i.e.they create and organism, i.e. CellsCells TissuesTissues OrgansOrgans Organs SystemsOrgans Systems OrganismsOrganisms
The Cell CycleThe Cell Cycle
Cell Cycle:Cell Cycle: The sequence of growth and division in The sequence of growth and division in
the cell.the cell.
A cell goes though two periods:A cell goes though two periods: A period of growth A period of growth A period of division A period of division
The Cell CycleThe Cell Cycle
Mitosis
1 hour
Rapid Growth and Metabolic Activity
9 hours
DNA Synthesis and Replication
10 Hours
INTERPHASE
Prepare for cell division2 hours
InterphaseInterphase
The busiest part of the cell cycleThe busiest part of the cell cycle Part IPart I: Cell grows and protein production : Cell grows and protein production
is high.is high.
Part IIPart II: Cell copies its chromosomes: Cell copies its chromosomes
Part III:Part III: Parts manufactured for cell Parts manufactured for cell division.division.
The Cell CycleThe Cell Cycle
The cell cycle is controlled by;The cell cycle is controlled by; Proteins Proteins EnzymesEnzymes Area – to – Volume RatioArea – to – Volume Ratio
Occasionally, cells lose control.Occasionally, cells lose control. Cancer, malignant growth resulting from Cancer, malignant growth resulting from
uncontrolled cell division. uncontrolled cell division.
Cancer – A mistake in the Cancer – A mistake in the cell cycle!cell cycle!
TumorsTumors Masses of tissue that deprive normal cells of Masses of tissue that deprive normal cells of
nutrients.nutrients.
Cancer is the second leading cause of Cancer is the second leading cause of death in the United States, exceeded death in the United States, exceeded only by heart disease. only by heart disease.
MeiosisMeiosis
Meiosis forms haploid daughter cells Meiosis forms haploid daughter cells from diploid parent cells. from diploid parent cells.
Meiosis is divided into two parts;Meiosis is divided into two parts; Meiosis IMeiosis I Meiosis IIMeiosis II
Meiosis IMeiosis I
SynapsisSynapsis Homologous Chromosomes line up Homologous Chromosomes line up
next to each other.next to each other.
Forming a structure called a Forming a structure called a tetradtetrad..
Meiosis IMeiosis I
Meiosis I is divided into four stages;Meiosis I is divided into four stages; Prophase IProphase I Metaphase IMetaphase I Anaphase IAnaphase I Telophase ITelophase I
Meiosis IMeiosis I
Prophase IProphase I Homologous Chromosomes are Homologous Chromosomes are
formedformed Spindle fibers formSpindle fibers form Tetrads are visible and have lined up Tetrads are visible and have lined up
along the equator. along the equator.
Meiosis IMeiosis I
Metaphase IMetaphase I Each tetrad becomes attached to the Each tetrad becomes attached to the
spindle fibers spindle fibers
Meiosis IMeiosis I
Anaphase IAnaphase I Homologous chromosomes are pulled Homologous chromosomes are pulled
apart. apart. One pair goes to the on polar end One pair goes to the on polar end
while the other goes to the other end.while the other goes to the other end.
Meiosis IMeiosis I
Telophase ITelophase I Cytokinesis takes place.Cytokinesis takes place. The cell divides. The cell divides.
Meiosis IMeiosis I
At the end of Meiosis I;At the end of Meiosis I; One chromosome from each parent cell is One chromosome from each parent cell is
present in the daughter cell. present in the daughter cell.
Meiosis I is a reductive division;Meiosis I is a reductive division; Reduce the chromosomes from diploid (2n) Reduce the chromosomes from diploid (2n)
to a haploid (n). to a haploid (n).
Meiosis IIMeiosis II
Each daughter cell produced in Each daughter cell produced in Meiosis I undergoes another Meiosis I undergoes another division.division.
Meiosis II is very similar to Mitosis Meiosis II is very similar to Mitosis except, it is not proceeded by a except, it is not proceeded by a replication of the chromosomes. replication of the chromosomes.
Meiosis IIMeiosis II
There are four stages;There are four stages; Prophase IIProphase II Metaphase IIMetaphase II Anaphase IIAnaphase II Telophase IITelophase II
Meiosis IIMeiosis II
Resulting in;Resulting in; Four daughter cells Four daughter cells Each daughter cell produced is Each daughter cell produced is
haploid.haploid. Each cell has four chromosomes.Each cell has four chromosomes. One from each of the homologous One from each of the homologous
pairs of parent cells.pairs of parent cells.
Meiosis IIMeiosis II
Prophase IIProphase II New spindle fibers formNew spindle fibers form around the around the
chromosomes.chromosomes.
Meiosis IIMeiosis II
Metaphase IIMetaphase II Chromosomes line up along the Chromosomes line up along the
equator.equator. Attach the centromere to the spindle Attach the centromere to the spindle
fibersfibers
Meiosis IIMeiosis II
Anaphase IIAnaphase II The centromere divides and the The centromere divides and the
chromatids separate.chromatids separate. Each chromatids becomes it on Each chromatids becomes it on
chromosomes with their own chromosomes with their own centromere. centromere.
Meiosis IIMeiosis II
Telophase IITelophase II The nuclear envelope forms The nuclear envelope forms
around each set of chromosomes. around each set of chromosomes. Cell undergoes Cytokinesis. Cell undergoes Cytokinesis.