Presentation on theme: "Recap on Cell Size cells are limited in their size because of 3 things: 1. Diffusion 2. DNA 3. Food Requirements Therefore, Cells have 2 methods of."— Presentation transcript:
1 Recap on Cell Sizecells are limited in their size because of 3 things:1. Diffusion2. DNA3. Food RequirementsTherefore, Cells have 2 methods of dealing with cell size:Altered ShapeCell DivisionWe are going to learn how cells Divide!
2 Cell Theory & Chromosomes Recall that Cell theory states “all cells come from preexisting cells.”Cell Division results in two cells that are identical to the original, parent cellChromosomes – “colored bodies” that contain genetic material.It is the identity of the cellAccurate transmission of chromosomes during cell division is critical.
3 The Cell Cycle Cell Cycle – sequence of growth and division of a cell Broken into 2 Parts:Interphase : GrowthMitosis : DivisionA cell spends most of its life in INTERPHASECell division is during mitosisOne final process, division of the cytoplasm, cytokinesis, takes place after mitosis.
4 Cell Cycle - Interphase During Interphase…Cell grows in sizeCarries on metabolismReplicates chromosomesComposed of 3 Phases:G1 : Chromosomes are not yet visible, rapid protein synthesis due to growthS : Chromosomes are replicated in the nucleus (sister chromatids)G2 : Chromosomes shorten & coil, protein synthesis prepares for Mitosis, centrioles prepare to make the mitotic spindle, cell organelles are replicated
5 Cell Cycle: Mitosis - Prophase There are 4 Stages of Mitosis1.) PROPHASEFirst and longest stageChromatin coils up into visible chromosomesSister Chromatids are visible (2 exact copies of DNA for the 2 new cells) from interphaseSister Chromatids are held together by a centromereNucleus begins to disappearNucleolus disintegratesAnimal Cells – Centrioles Migrate to the poles for chromatin separationSpindle forms – for sister chromatid separation. In Plant cells the spindle forms without centrioles.
6 Chromatin – long strands of DNA wrapped around proteins, it only becomes chromosomes for replication and protein synthesis.Centromere – Structure that holds sister chromatids together. Plays a role in chromosome movement during mitosis. By their characteristic location, centromeres also help scientists identify and study chromosomes.
7 Cell Cycle: Mitosis - Metaphase During Metaphase…Short second phaseDoubled chromosomes become attached to the spindle fibers by their centromeresChromosomes are pulled by the spindle fibersBegin to line up on the midline or equator of the spindleEach sister chromatid is attached to its own spindle fiberOne spindle fiber extends to one pole, the other to the opposite poleEnsures that each new cell receives an identical and complete set of chromosomes.
8 Cell Cycle: Mitosis - Anaphase During Anaphase…Third phase of mitosisSeparation of sister chromatids at the beginningCentromeres split apartChromatid pairs from each chromosomes separate from each otherChromatids are pulled apart by the shortening of the microtubles in the spindle fibers
9 Cell Cycle: Mitosis - Telophase In Telophase…The fourth and final stageBegins as chromatids reach the opposite poles of the cellMany of the Mitotic changes that took place are reversing for the two new cellsChromosomes unwind for protein synthesisSpindle breaks downNucleolus reappearsNew nuclear envelope forms around each set of chromosomesA new double membrane begins to form around the 2 new nuclei
10 Mitosis - CytokinesisFollowing telophase, the cell’s cytoplasm divides in a process called CytokinesisIn Animal Cells – plasma membrane pinches in along the equatorIn Plant Cells – a cell plate is laid down across the cell’s equator. A cell membrane forms around each cell, and new cell walls form on each side of the cell plate until separation is complete.
11 Your Turn!Place the following images in order of Mitosis with numbers, and give the name of the cycle. Let interphase be step 5.
12 How did you do? 2 - Metaphase 1 - Prophase 4 - Telophase 3 - Anaphase 5 - Interphase
13 Results of Mitosis Mitosis gives genetic continuity Daughter cells will carry out the same process or job as the parent cellResults in groups of cellsAtoms form MoleculesMolecules form CellsCells form TissuesTissues form OrgansOrgans form Organ systemsOrgan Systems form an OrganismRemember! The Cell is STILL the most basic unit of organization.