Cell Growth and ReproductionBiology
Cell ReproductionCell division in necessary to form multi-cellular organisms.Asexual Reproduction:Production of offspring from one parent cell.Sexual Reproduction:Formation of offspring from the union of two gamete cells .
Asexual ReproductionSteps:Chromosomes duplicate (called replication)Both attach to a site located in the cellThey are forced apart.Cell membrane constricts them till they separate.
ChromosomesChromatids: Long strands of DNA.Chromosomes:Made of two sister chromatids.Held together by a centromere
Diploid (2n) CellsA cell with two of each kind of chromosomes are called Diploid Cells.
Haploid (n) CellsA cell with one kind of each chromosome is called a Haploid cell.
MitosisCells undergo mitosis as they reach their maximum cell size. There are four steps in mitosis:ProphaseMetaphaseAnaphaseTelophase
Mitosis:Stage 1 Prophase.Chromatids coil up into visible chromosomes.Nucleus DisappearsCentrioles migrate to the polar ends of the cellSpindle Fibers begin to form.
Mitosis:Stage 2 MetaphaseChromosomes become attached to the spindle fibers by their centromeres.They are lined up across the center of the cell.
Mitosis:Stage 3 AnaphaseSister chromatids begin to separateChromatids are pulled apart, and separate from each other.
Mitosis:Stage 4 TelophaseNew cells prepare for their new existence.Chromosomes uncoil and direct metabolic activitySpindle Fibers break downNucleolus reappearsDouble membrane forms between them
MitosisCytokinesisAnimals Plasma Membrane pinches in along the equator of the cell.
MitosisCytokinesisPlants - Cell Plate is laid across the equator.Cell walls form around the plate
Results of MitosisAs a result, Each daughter cell receives and exact copy of the chromosomes present in the parent cell. They copy their chromosomes during Interphase.They become a diploid cell 2nThe process can then start over.
Results of MitosisProcess that guarantees that genetic continuity.The two new cells formed will carry out the same functions of the parent cell. They will grow and divide just like the parent cells.
Results of MitosisAs a result of cell division we have groups of cells working together, until they create and organism, i.e.CellsTissuesOrgansOrgans SystemsOrganisms
The Cell CycleCell Cycle:The sequence of growth and division in the cell.A cell goes though two periods:A period of growth A period of division
The Cell CycleMitosis 1 hourRapid Growth and Metabolic Activity9 hoursDNA Synthesis and Replication10 HoursINTERPHASEPrepare for cell division2 hours
InterphaseThe busiest part of the cell cyclePart I: Cell grows and protein production is high.
Part II: Cell copies its chromosomes
Part III: Parts manufactured for cell division.
The Cell CycleThe cell cycle is controlled by;Proteins EnzymesArea to Volume Ratio
Occasionally, cells lose control.Cancer, malignant growth resulting from uncontrolled cell division.
Cancer A mistake in the cell cycle!TumorsMasses of tissue that deprive normal cells of nutrients.Cancer is the second leading cause of death in the United States, exceeded only by heart disease.
MeiosisMeiosis forms haploid daughter cells from diploid parent cells.
Meiosis is divided into two parts;Meiosis IMeiosis II
Meiosis ISynapsisHomologous Chromosomes line up next to each other.
Forming a structure called a tetrad.
Meiosis IMeiosis I is divided into four stages;Prophase IMetaphase IAnaphase ITelophase I
Meiosis IProphase IHomologous Chromosomes are formedSpindle fibers formTetrads are visible and have lined up along the equator.
Meiosis IMetaphase IEach tetrad becomes attached to the spindle fibers
Meiosis IAnaphase IHomologous chromosomes are pulled apart. One pair goes to the on polar end while the other goes to the other end.
Meiosis ITelophase ICytokinesis takes place.The cell divides.
Meiosis IAt the end of Meiosis I;One chromosome from each parent cell is present in the daughter cell. Meiosis I is a reductive division;Reduce the chromosomes from diploid (2n) to a haploid (n).
Meiosis IIEach daughter cell produced in Meiosis I undergoes another division.
Meiosis II is very similar to Mitosis except, it is not proceeded by a replication of the chromosomes.
Meiosis IIThere are four stages;Prophase IIMetaphase IIAnaphase IITelophase II
Meiosis IIResulting in;Four daughter cells Each daughter cell produced is haploid.Each cell has four chromosomes.One from each of the homologous pairs of parent cells.
Meiosis IIProphase IINew spindle fibers formaround the chromosomes.
Meiosis IIMetaphase IIChromosomes line up along the equator.Attach the centromere to the spindle fibers
Meiosis IIAnaphase IIThe centromere divides and the chromatids separate.Each chromatids becomes it on chromosomes with their own centromere.
Meiosis IITelophase IIThe nuclear envelope forms around each set of chromosomes. Cell undergoes Cytokinesis.
Meiosis Why?The result; Cells used for reproductionSperm CellsOvum Cells