I. MITOSIS A. Cell Division: 1. Needed for normal growth, repair, & development 2. Occurs in somatic cells (body cells) 3. Daughter cells have an exact copy of DNA of parent cell 4. Each parent cell produces 2 daughter cells

B. Why Do Cells Divide? 1. Volume Limit: a) food intake b) waste removal 2. Volume to Surface Area Ratio -Volume increases much more rapidly than surface area as the cell grows in size Will do lab on Volume to Surface Area ratio. Cells can only take in food/get rid of waste at the surface of cells. If the volume to surface area ratio is too big, cells cannot take in enough food or get rid of all the waste. Pause to do examples with cube dimensions, SA, vol, ratio

II. Cell Cycle

A. Interphase 1. Not part of Mitosis 2. 90 % time here 3. Carries out metabolic processes: Making new molecules & organelles Normal growth/development Cell prepare for division 4. DNA replication 5. Chromosomes are not distinguishable (chromatin) 6. Prepares for cell division Chromosomes contain the DNA/genetic material. Called chromatin when not consolidated

1. G1 phase (normal growth) 2. S phase (synthesis) 7. Cell Cycle: 1. G1 phase (normal growth) 2. S phase (synthesis) 3. G2: prepares to divide 4. Mitosis/Cytokineses G1 and G2 the cell grows and functions normally DNA replicates in S phase

Mitosis Begins Cell Cycle Continues

B. Prophase 1. First stage of mitosis 2. Chromosomes appear (shorten & thicken = sister chromatids) 3. Centrioles, spindle fibers appear 4. Nuclear membrane dissolves Sister chromatids contain two copies of identical DNA (replicated during S phase)

C. Metaphase 1. Chromosomes line up at the equator Spindle fibers attach to each chromosome at the centromere, the center portion holding the sister chromatids together

D. Anaphase 1. Chromosomes separate and migrate to the opposite ends of the cell 1 copy of DNA to each end of the cell

E. Telophase 1. Reorganization a) spindle fibers disappear b) nuclear membrane forms 2. Chromosomes lengthen & disappear 3. Cytoplasm splits (cytokinesis) into two daughter cells Cell Plate forms for plant cells Chromosomes turn back into chromatin

Mitosis in Animal Cells Prophase – can see chromosomes Prometaphase – in between the two phases, students do not need to know Metaphase – can see spindle fibers and the chromosomes lined up Anaphase – Chromosomes are separating Telophase – spindle fibers are starting to disappear, cell is starting to split

Mitosis in Whitefish Blastula

Cytokinesis in Plant Cells Thick line down the middle is the cell plate (unique to mitosis in plants)

Mitosis in Plant Cells

Mitosis in Onion Root Tip Each cell goes through mitosis at different times, this picture shows several different stages of mitosis

F. Significance 1. TWO Daughter cells 2. Identical DNA to parent cell 3. Healing Growth Mitosis Animation Mitosis Animation has music but no narration, lasts about 1 minute

G. Cell Cycle From Individual Daughter cell  complete cell division Two Parts: a. Interphase: G1, S, G2 b. Mitosis/Cytokinesis Reminder: Cell Cycle is Interphase + Mitosis. Mitosis does not include interphase, it is just the process of cell division

H. Role of the Cell Cycle A. Nearing the end of G1, two options: 1. Continue cell cycle; committed to initiating DNA replication OR 2. GO (resting phase): cell remains viable and metabolically active but are nonproliferative (don’t reproduce) 3. Cancer cells avoid entering GO or go through very quickly

B. Tumors and Cancer 1. Tumor: mass of cells formed from out of control cell reproduction 2. Benign tumors: abnormal mass of normal cells -remain at original site 3. Malignant tumor: abnormal rapidly dividing cells 4. Metastasis: spread of cancer cells Cancer Cell Explanation Metastasis Video Cancer Cell Explanation – 20 seconds Metastasis video – 2:12

C. Protein p53 (Tumor Suppressor Gene) 1. Protein to control cells w/damaged DNA: a. code to stop cell cycle b. repair DNA c. program cell death 2. Mutation of p53 gene a. found in many cancers b. does not stop mitosis P53 is a gene that recognizes damaged cells and stops the cell division (mitosis). It initiates either cell repair or cell death

Can ignore bottom row of pictures