1. Cell Division

2. Why Cells Make More Cells 1. Most cells go through a series of changes in order to maintain homeostasis. 2. Cells need to reproduce (divide) when their surface area can no longer supply the much larger volume with nutrients and get rid of wastes. Surface Area (length x width x 6) Volume (length x width x height) Ratio of Surface Area to Volume

3. Vocabulary 1. Chromatin: the relaxed, uncoiled state of the chromosome 2. Chromatid: one of two identical “sister” parts of a duplicated chromosome 3.Chromosome: threadlike structures within the nucleus containing genetic information that is passed on from generation to generation 4. Centromere: chromosome region that joins 2 sister chromatids A: centromere chromo─ color ─soma: body ─id: self, body centro─ center ─mere: part B: chromatids

4. Chromosomes 1. Chromosomes: made up of DNA & proteins 2. Carry the cell’s coded genetic information 3. Different organisms have a different number of chromosomes Fruit flies have 8 chromosomes in each body cell Frogs have 26 chromosomes in each body cell Humans have 46 chromosomes in each body cell

5. Cell Cycle 1. Cell cycle: Sequence of events between the time a cell divides to form 2 daughter cells & the time those 2 cells divide 2.Consists of Interphase and M-phase (Mitosis & Cytokinesis ) 3.G 0 ─ cells that exit the cell cycle

6. Interphase: 3 Phases 1. G 1 phase: Growth Phase a.Cell performs all life’s activities: protein synthesis, waste removal, organelle synthesis, etc. 2. S phase: DNA Replication a.DNA makes a copy of itself b.Produces 2 identical sets of chromosomes 3. G 2 phase: Preparation a.Cell produces centrioles & spindle fibers needed to move the chromosomes

7. Mitosis Discovered Walther Flemming first discovered mitosis in 1870 and reported is discovery of chromosomes and mitosis in 1882. Metaphase in a salamander cell drawn by Walther Flemming from a stained slide.

8. Mitosis Review 1. Two main stages of the M-phase a. Mitosis: division of the nucleus b. Cytokinesis: division of the cytoplasm 2. Produces 2 cells called daughter cells a. Cells are genetically identical 3. Mitosis is source of new cells for a. Growth b. Development c. Repair d. Replacement of old cells 4. Cells that go through mitosis: skin, bone, muscle, liver 5. Cells that RARELY go through mitosis: nerve cells Normal red blood cells only live for 120 days. Then they die & stem cells make new ones.

9. Mitosis 1.Described as movement of chromosomes 2.Continuous series of events 3.Divided into four phases so that it is easier to understand Cell Cycle

10. Diploid verses Haploid Di─double Haplo─single -oid:like 23 Sperm cell 23 Egg cell 46 Fertilized Egg cell Fertilization Haploid: 1n; 1 set of chromosomes The egg and sperm cell are haploid Diploid: 2n; 2 sets of chromosomes The fertilized egg cell is diploid Develops into All of the cells that make up the organism are diploid Each kind of cell: Skin Muscle Bone Nerve Are ALL DIPLOID

11. 1. Normal cells contain check points to regulate the cell cycle, & stop at appropriate check points. 2. Cancerous cells do not respond to check points and continue rapidly through the cell cycle. This results in masses of undefined cells called tumors. 3. Cancer cells do not mature; they become more immature. Do not enter into G 0 Cancer Cells