5.2 Mitosis and Cytokinesis Purpose of Cell Division in Multicellular Organisms Growth – get bigger by making more cells Replacement – replace cells that die Repair – replace cells that get damaged Maintain size limit (surface area to volume ratio) Asexual Reproduction Purpose of Cell Division in Unicellular Organisms Asexual reproduction Make new organism

Cell Division – in Eukaryotes  2 Types of cell division:  1. Mitosis: division of somatic cells  2. Meiosis: creation of new sex cells Sperm cellsHuman egg cell Pancreatic cells

Cell Division - Prokaryotes  Binary Fission – asexual reproduction method to make a new organism

Warm Up to ……Cell Division Name the 3 types of cell reproduction and their final product (number and type of cell made) Which two types make clones genetically same Which makes genetically different cells Haploid vs Diploid Which chrom number means 2 of each chrom type ? Which means only 1 of each chrom type? Which do sex cells have? ?

5.2 Mitosis and Cytokinesis It’s the CELL CYCLE !!

Cell Cycle  Most cells have a life cycle that includes:,  Growth  Doing its job  Dividing INTERPHASE

2 Major Stages of the Cell cycle  Interphase –  Cell carries out its special job, Prepares for Cell division by doublin’ all of its organelles and chromosomes  Cell Division (M phase)  Evenly divides the chromosomes and other cell contents into two separate cells

Cell Cycle - Interphase  The longest phase in the cell cycle is interphase.  Interphase has 3 stages: G 1, S, and G 2. G 1, S, and G 2.

G1 – Gap 1  Longest period of cell’s life  Cell carries out it job  Grows in size  Must pass 1 st critical checkpoint before entering “S” phase  Cells that aren’t destined to divide enters G 0 stage.  Ex. Nerve cells

S -“Synthesis ”  DNA replicates –creates a doubled chromosome each strand is sister chromatid  The DNA in each strand is genetically identical condensed chromosome chromatid centromere

G 2 - Gap 2  2nd checkpoint – ensure DNA and organelles replicate properly to prepare for division

Why is Interphase Important  Interphase is NOT part of cell division  BUT  Interphase processes are important in preparing the cell to divide properly

Cell Division (M or Mitosis)

2 Stages of Cell Division  Mitosis – Division of the chromosomes  into 2 new nuclei 4 Stages:  Prophase  Metaphase  Anaphase  Telophase

  Cytokinesis – Division of the cytoplasm into 2 new cells.

Length of Time Cell spends in the Cell Cycle Length of Time Cell spends in the Cell Cycle  Varies by cell type.  Skin cells and intestinal lining cells frequently divide  Other cells like brain and nerve rarely, if ever divide – they enter the G 0 stage.

5.2 Mitosis and Cytokinesis KEY CONCEPT Cells division occurs through mitosis and cytokinesis.

Parent cell centrioles spindle fibers centrosome nucleus with DNA Longest phase of cell cycle Cell grows and does its job (metabolically active) Chromatin in nucleus Nucleus and Nucleus visible Duplicates organelles in “G1” phase and chromosomes in “S” phase Interphase

5.2 Mitosis and Cytokinesis Chromosomes doubled in S phase Each half is called a chromatid. Sister chromatids are held together at the centromere. Condensed, duplicated chromosome chromatid centromere

5.2 Mitosis and Cytokinesis Draw Interphase

5.2 Mitosis and Cytokinesis Draw Interphase Draw Interphase

5.2 Mitosis and Cytokinesis INTERPHASE ends MITOSIS begins: 4 Stages of Mitosis: Prophase Metaphase Anaphase Telophase

PROPHASE Longest stage of Mitosis Chromosomes condense (coil up) and become visible Nuclear membrane and nucleolus break down Centrioles move to opposite poles of the cell Asters and spindles fibers form between poles

Chromosomes condense and can be seen Chromatin Chromosomes Chromatin Chromosomes

5.2 Mitosis and Cytokinesis Early Prophase

Late Prophase  Nuclear membrane disappears.

Draw Prophase

Prophase

Prophase Centriole 2

Prophase Spindle fibers

Prophase Aster 4 5 Centriole Spindle fibers

Prophase Aster Sister chromatids 5 Centriole Spindle fibers

Prophase Aster Sister chromatids Centromere Centriole Spindle fibers

5.2 Mitosis and Cytokinesis METAPHASE Centriole Shortest phase of mitosis Chromosomes line up at the cell’s equator Spindle fibers attach to centromeres on the chromosomes. Spindle fibers

5.2 Mitosis and Cytokinesis METAPHASE

Draw Metaphase

ANAPHASE Centromeres divide and the sister chromatids split apart and move to opposite poles. Individual chromatids now called Chromosomes

5.2 Mitosis and Cytokinesis Anaphase

Draw Anaphase

Telophase   Chromosomes uncoil.   The nuclear membrane re-forms around the two sets of chromosomes.   Two new nuclei formed  END OF MITOSIS

Draw Telophase

Cytokinesis   Cytoplasm divides   Two separate daughter cells are formed   Occurs differently in animal and plant cells

Cytokinesis in Animal Cells   Animal cells have a flexible cell membrane   Cytoplasm pinches in creating a Cleavage Furrow   Two separate Daughter Cells are formed Cleavage furrow in a dividing frog cell.

Cytokinesis in Plant Cells  In plant cells, a Cell Plate forms and creates a cell wall that seperates the cytoplasm into 2 separate daughter cells Cell Plate forming

ANIMAL vs. PLANT MITOSIS  ANIMAL CELL  Centriole and aster present  Daughter cells separated by cleavage furrow  PLANT CELL  No visible centriole or aster  Daughter cells separated by cell plate

5.2 Mitosis and Cytokinesis Cytokinesis – Cytoplasm Division Animal Cell Cleavage Furrow Plant Cell Cell Plate

5.2 Mitosis and Cytokinesis

Identify each of the following cell cycle stages

5.2 Mitosis and Cytokinesis Let’s Review the Events of the Cell Cycle Cell Cycle and Mitosis 3D Video Cell Cycle Video Cell Cycle Video #2 Cell Cycle Video #3 Cell Cycle tutorial #1Cell Cycle tutorial Cell Cycle tutorial #2Cell Cycle tutorial Animal Cell Division Plant Cell Division#1Plant Cell Division Plant Cell Division #2 Meiosis in 3D

5.2 Mitosis and Cytokinesis

1.In which stage of the cell cycle do cells grow, do their job 2.In which stage do cells create 2 new nuclei each with a copy of the same chromosomes as the parent cell 3.Which stage of the cell cycle does the cytoplasm divide to create 2 separate cells that are genetically identical 4.If a cell has 8 chromosomes how many in the new cells? 5. Write the correct order of phases in Mitosis 5. What stage is this and what are the chromosomes doing?

Mitosis: Can you name the stages?

Prophase

Mitosis: Can you name the stages? Prophase Metaphase 3 4 5

Mitosis: Can you name the stages? Prophase Metaphase Anaphase 4 5

Mitosis: Can you name the stages? Prophase Metaphase Anaphase Telophase 5

Mitosis: Can you name the stages? Prophase Metaphase Anaphase Telophase Cytokinesis

 Phases of mitosis - IPMATC I P assed M y Algebra T est C HACHING! IPMATCIPMATC

Cell Cycle  A typical cell goes through a process of growth, development, and reproduction called the cell cycle.  Most of the cycle is called interphase. INTERPHASE

Cell Cycle  The longest phase in the cell cycle is interphase.  The 3 stages of interphase are called G 1, S, and G 2.

Cell Cycle  Cells spend most of their time in G 1 : it is the time when the cell grows and performs its normal function.  Control of cell division occurs in G 1 : a cell that isn’t destined to divide goes into G 0.

Cell Cycle  The S phase (“Synthesis”) is the time when the DNA is replicated. Parent strands Daughter strands

Cell Cycle  G 2 is the period between S and mitosis.  DNA replication is checked and the cell is getting ready to divide.