February 16, 2012 BellRinger  You have learned that mitosis is important for asexual organisms, how might this type of cell division be beneficial for you and other organisms? Objectives  List, describe, and recognize the various stages of mitosis Homework  None

Why divide? Continuity  Asexual reproduction Growth (zygote → multicellular org) Repair, renewal, replacement Do all cells divide? Do they divide at the same rate?

Cell Cycle A sequence of cell growth and division Numerous factors control when cells divide 2 major phases:  Interphase growing and replication of DNA  Cell Division Mitosis- division of chromosomes Cytokinesis- division of cytoplasm

Cell Cycle How much time does the cell spend in Interphase? Mitosis?

BellRinger Quiz(on looseleaf) Place the following stages of mitosis in the correct order

Answer 2,3,1,4,5&6 Prophase (prepare) Anaphase (apart) Telophase (two) Cytokinesis Metaphase (middle) Interphase &

Mitosis Review the stages of mitosis by putting the cards in the correct sequence.  DO NOT USE YOUR NOTES OR YOUR BOOK.  Predict the sequence just by examining what is happening in the pictures  After your sequence is approved, write down what you see happening in each picture in your notebook Cellular division that produces two identical daughter cells Used by asexual organisms for reproduction When would your body cells need to divide using mitosis? Mitosis movie

February 20, 2012 BellRinger  Previous slide Objectives  List, describe, and recognize the various stages of mitosis  Determine the consequences when mitosis is not controlled Homework  Be able to draw, recognize and explain the steps of mitosis for your real quiz tomorrow

Getting the right stuff Why divide?  Reproduction, growth, repair What is passed on to daughter cells?  exact copy of genetic material = DNA mitosis  organelles, cytoplasm, cell membrane, enzymes cytokinesis

Maintaining Chromosome Number Chromosome number remains the same from one generation to the next mitosis, cytoplasmic division chromosome (unduplicated) in daughter cell at interphase chromosome (unduplicated) in daughter cell at interphase chromosome (unduplicated) in cell at interphase same chromosome (duplicated) in interphase prior to mitosis

Overview of mitosis interphaseprophase(pro-metaphase) metaphaseanaphasetelophase cytokinesis I.P.M.A.T.

Interphase Nucleus well-defined  DNA loosely packed in long chromatin fibers Prepares for mitosis  replicates chromosome DNA & proteins  produces proteins & organelles

Prophase prepares Cell prepares to divide DNA is packaged into movable units called chromosomes Nuclear membrane breaks down Centrioles move to opposite ends of the cell.

Metaphase middle The chromosomes migrate to the middle of the cells. Spindle fibers attach to the chromosomes.

Anaphase apart Chromosomes are pulled apart as the spindle fibers shorten toward the poles. One copy of each chromosome goes to each side of the cell.

Telophase two The two new cells begin to pinch off at the center.

Cytokinesis Cytoplasmic Division Usually occurs between late anaphase and end of telophase Two mechanisms  Cell plate formation (plants)  Cleavage (animals)

Cytokinesis: Animal Cell Figure 9.9 Page 159 Cleavage furrow

Cytokinesis: Plant Cells Figure 9.8 Page 158 Cell Plate Formation

Mitosis: plant vs. animal cells Plant cellAnimal Cell CentriolesAbsentPresent Cytokinesis Cell plate formation Cleavage furrow

Result of Mitosis Cytoplasm and organelles divided between the two cells. (cytokinesis) Mitosis results in two identical daughter cells. DNA must be replicated before cells divide again.

Learning Check If the cell of a fruit fly starts with 4 chromosomes, how many chromosomes will each of the daughter cells have after mitosis? (draw a diagram if you need to)

Control of the Cell Cycle Internal Controls  Chemical controls  Checkpoints External Controls  Contact inhibition What happens if these control mechanisms fail?

Loss of Normal Growth Control Cancer cell division Fourth or later mutation Third mutation Second mutation First mutation Uncontrolled growth Cell Suicide or Apoptosis Cell damage— no repair Normal cell division

Example of Normal Growth Cell migration Dermis Dividing cells in basal layer Dead cells shed from outer surface Epidermis

The Beginning of Cancerous Growth Underlying tissue During the development of skin cancer, the normal balance between cell division and cell loss is disrupted

Tumors (Neoplasms) Underlying tissue Tumors increase in size because new cells are being produced in greater numbers than needed.

Invasion and Metastasis 3 Cancer cells reinvade and grow at new location 1 Cancer cells invade surrounding tissues and blood vessels 2 Cancer cells are transported by the circulatory system to distant sites

Malignant versus Benign Tumors Malignant (cancer) cells invade neighboring tissues, enter blood vessels, and metastasize to different sites Time Benign (not cancer) tumor cells grow only locally and cannot spread by invasion or metastasis

Why Cancer Is Potentially Dangerous Melanoma cells travel through bloodstream Melanoma (initial tumor) Brain Liver Cancer cells in the liver would be called metastatic melanoma, not liver cancer. Metastases share the name of the original (“primary”) tumor

Summary (on loose leaf) What is cancer and how are cancerous cells different from normal cells? Homework  Be able to draw, recognize and explain the steps of mitosis for your real quiz tomorrow