When you see a newborn baby, is it hard for you to imagine that just nine months ago, that baby was a single cell?

1. Something to think about... When you see a newborn baby, is it hard for you to imagine that just nine months ago, that baby was a single cell? When you see a towering oak tree, can you believe that it was once a measly acorn? When you mow the lawn on Saturday, can you believe that by next Saturday, you have to do it again? Can you believe that every second, your body makes 25 million new cells?

2. Cell Growth and Reproduction

3. What Limits Cell Size? Why can’t organisms be just one giant cell? 1 Diffusion 2 DNA Content 3 Surface Area to Volume Ratio

4. Diffusion  = Mitochondrion Waste Waste Oxygen   Glucose  Cells can metabolize only as quickly as they receive raw materials.  An average-sized cell with a diameter of 20um will receive supplies in a fraction of a second. What if the cell were 20cm in diameter? So long, big cell!

5. DNA Content  Most cells contain only one nucleus responsible for programming all metabolism. DNA RNA  If the ribosomes don’t receive enzyme and protein-making instructions from the RNA, guess what? So long, big cell!

6. Surface Area-to-Volume Ratio  As a cell’s size increases, its volume increases much faster than its surface area. Volume l x w x h Surface Area l x w x # sides 3 cm 2 cm 1 cm3 6 cm2 1 cm 27 X 9 X 8 cm3 24 cm2 You Know! So long, big cell! 27 cm3 54 cm2

7. So, what must the cell do? DIVIDE

8. Functions of Cell Division • In multicellular eukaryotes: • Growth and development • Replace old, worn-out and dying cells and tissues • Sexual reproduction – making of gametes, or sex cells (sperm and egg) • In unicellular prokaryotes: • Asexual reproduction

9. Types of Reproduction • Asexual Reproduction • Formation of offspring from one parent • Offspring are genetically identical to the parent • Leads to lack of genetic diversity among offspring ~ disadvantage in changing environment • Types include: • Binary fission – bacteria • Fragmentation – starfish, Planaria • Budding - sponges

10. Binary Fission Division of a prokaryotic cell into two offspring cells

11. Types of Reproduction • Sexual Reproduction • Formation of offspring by uniting gametes from two parents • Offspring are genetically different from the parents • Increases variation in the population by making possible genetic recombination

12. Eukaryotic Cell Reproduction • Before cell division, DNA coils tightly around histones (proteins) and forms chromosomes

13. Chromosome Structure Chromosomes (rod-shaped structures made of DNA and protein) must be duplicated in order for each daughter cell to receive identical copies of the parental chromosomes; each chromosome consists of two identical halves called sister chromatids held together by a centromere

14. Humans’ somatic, or body cells, have 23 pairs of chromosomes (46 = diploid or 2n number) – first 22 pair are autosomes; last pair are sex chromosomes XX=female XY=male The two copies of each autosome are called homologous chromosomes, or homologues (same size and shape and carry genes for same traits Sex Chromosomes and Autosomes

15. Chromosome numbers of various species

16. Cell Cycle – Cell Division in Eukaryotes G1, S, and G2 = Interphase Prophase, Metaphase, Anaphase, Telophase = Mitosis IPassed My Algebra Test G1 -- Period of cell growth before DNA is duplicated S -- period when DNA is duplicated Telophase G2 -- period after DNA is duplicated; cell prepares for division; end of interphase Anaphase Metaphase Prophase

17. Mitosis Overview www.biologycorner.com/images.html

18. Interphase – G1, S, G2  The cell is engaged in metabolic activity and performing its preparation for mitosis. Chromosomes are not clearly visible in nucleus, but the nucleolus may be visible. Centrioles (or microtubule organizing centers) may be visible during this phase. nucleus nuclear membrane chromatin

19. Interphase – G1, S, G2  In G1 or first growth phase, cells mature and increase in size by making more cytoplasm and organelles S or Synthesis phase follows G1 and results in the replication of genetic material  Cell makes all structures needed to divide in G2 or second growth phase nucleus nuclear membrane chromatin

20. Prophase Chromatin in the nucleus begins to condense and becomes visible in light microscope as chromosomes. Nucleolus disappears. Centrioles in animal cells begin moving to opposite ends of the cell and fibers extend from the centromeres.

21. Interactive Eye, LLC (1997) [Site Name] Prophase • Type your welcome message here. You can make this a long message, or something short. Be sure to include a brief description of the type of things that can be found at this location. Custom Topic A Custom Topic B Vital Statistics Favorite Links to Visit

22. Metaphase Spindle fibers align the chromosomes along the middle of the cell nucleus, or equatorial plate. • This organization ensures that in the next phase, each new nucleus will receive one copy of each chromosome.

23. Interactive Eye, LLC (1997) Metaphase

24. Anaphase  The paired chromosomes separate at the centromere and move to opposite sides of the cell; after chromatids separate, they are considered to be individual chromosomes.

25. Interactive Eye, LLC (1997) Anaphase

26. Telophase  Chromatids arrive at opposite poles of the cell and new membranes form around the daughter nuclei.  Chromosomes uncoil and are no longer visible under the light microscope. Cytokinesis begins. Cell Plate or Cleavage Furrow

27. Interactive Eye, LLC (1997) Telophase

28. Cytokinesis In animal cells, cytokinesis results when a cleavage furrow forms and pinches the cell in two. In plant cells, cytokinesis occurs when vesicles from the Golgi apparatus fuse to form a cell plate.

29. Interactive Eye, LLC (1997) Cytokinesis

30. Animal Cell - Mitosis

31. Plant Cell - Mitosis

32. Mitosis Video Review • Video Link #1 - Youtube • Video Link #2 – Cells Alive • Video Link #3 – DNAtube

33. Cell Reproduction  Following the completion of the cell cycle, two daughter cells result, with the same number of chromosomes as the parent cells. 46 46 14 46 14 46 46 46 46 46 14 14 HUMAN GORILLA GARDEN PEA

34. So… What Are The Results? Genetic continuity, i.e., two new cells with chromosome sets identical to the parent cell. Daughter cells will carry out the same cellular processes and functions as their parent cell and will grow until the limitations of cell size force them to divide.

35. Control of Cell Division • Three checkpoints control division • Cell growth (G1) checkpoint: proteins control whether the cell will divide • DNA synthesis (G2) checkpoint – DNA repair enzymes check results of DNA replication;if checkpoint is passed, proteins will signal the cell to begin mitosis • Mitosis checkpoint – if a cell passes, proteins signal the cell to exit mitosis and enter G1 again

36. When Control is Lost • If mutation occurs in one of the genes (p53 gene) that regulates cell growth and division, proteins may not function properly • This may lead to cancer, or the uncontrolled growth of cells • Environmental influences may also play a role, e.g., UV rays, radiation, X-rays • ONCOLOGY – study of cancer

37. To Review... • Limits of Cell Size • Diffusion • DNA Content • Surface Area-to-Volume Ratio • Cell Cycle • Interphase • Mitosis (Nuclear Division) • Prophase, Metaphase, Anaphase, Telophase • Cytokinesis (Cytoplasmic Division)

38. During which stage does DNA replication occur? A. Prophase. B. Anaphase. C. Metaphase. D. Interphase.

39. Name the Following Stages Anaphase Prophase Metaphase Telophase

40. Which stage of mitosis is seen in the pictured cell? A. Anaphase. B. Prophase. C. Telophase. D. Interphase.

41. Which diagram most correctly represents the process of mitosis?

42. Which answer gives the stages of mitosis in proper chronological order? A.Anaphase prophase  metaphase  telophase. B. Metaphase  anaphase  telophase  prophase C. Prophase  metaphase  anaphase  telophase. D. Interphase  prophase  metaphase  anaphase  telophase.