Chapter5: The Cell Cycle and Mitosis

1. Chapter5: The Cell Cycle and Mitosis

2. The cell cycle and mitosis happens in the nucleolus of the cell (the dense section of nucleus)

3. The Cell Cycle  A. The Role of Cell Division • Why do cells divide? • Growth • Reproduction • Replacement of dying cells – skin, RBC • Reproduction in multi-cellular organisms – gamete formation (meiosis) • In the case of growth, why divide, rather than simply get bigger? • Surface:volume ratio constraints

4. The Cell Cycle --> Interphase • 1. G1 Phase 1st growth phase • 2. S Phase  DNA duplicated • G2 Phase  Final growth phase • Purpose of the first three phases (Interphase) – to duplicate cell contents; 90% of the cell’s growth cycle • Mitosis • Purpose of Mitosis – to divide the genetic material into exact two halves • 5. Cytokinesis • Purpose of Cytokinesis – to divide all other contents (except nucleus) into two cells

6. Interactive Cell cycle • http://www.cellsalive.com/cell_cycle.htm

8. Create a concept map • Use pages 153-155 to create a concept map explaining the cell cycle. • Start by drawing/tracing the drawing on page 153. • Label each step with information about the step. • Draw the arrows that separate each step and use colour to colour in your cell cycle drawing. • 4 marks for each step’s information (5 steps) • 5 marks for colour and clarity. • Due Monday /25

11. Important Notes DNA wraps some special proteins to form more stable structure called chromosomes Chromosome are found inside nucleus Human - 46 chromosomes, 23 pairs (1 set of 23 from egg, 1 set of 23 from sperm) Gene is a segment of DNA that is responsible for controlling a trait Each chromosome contains thousands of genes (these make up our traits)

12. Types of cell division • Mitosis (this chapter): • Growth, development & repair • Asexual reproduction (creates identical cells) • Occurs in body cells • Meiosis (next chapter): • Sexual reproduction (yields different cells) • Occurs in specific reproductive cells

14. Process of mitosis Aim: Two identical daughter cells exact copy of mother cell formed Requirements – the whole DNA must be copied exactly

15. Phases of Mitosis 1. Prophase 2. Metaphase 3. Anaphase 4. Telophase

18. Prophase • - Chromatin condenses, this causes the chromosomes to begin to become visible • Centrosomes separate, moving to opposite ends of the nucleus • The centrosomes start to form a framework used to separate the two sister chromatids called the mitotic spindle, that is made of microtubules • - Nucleolus disappears

23. 2. Metaphase - Chromosomes align on an axis called the metaphaseplate - Note: the spindle consists of microtubules, one attached to each chromosome

26. 3. Anaphase - Each centromere splits making two chromatids free - Each chromatid moves toward a pole - Cell begins to elongate, caused by microtubules not associated with the kinetochore

28. 4. Telophase • Formation of nuclear membrane and nucleolus • Short and thick chromosomes begin to elongate to form long and thin chromatin • Formation of the cleavagefurrow - a shallow groove in the cell near the old metaphase plate • Cytokinesis = division of the cytoplasm

31. Mitosis

32. Mitosis in an onion root

33. Asexual Reproduction • Only one parent is required to make offspring • Offspring are genetically identical to parents • Genetically identical organisms are called Clones • Mother cells create identical daughter cells

34. Binary fission in bacteria Not the best method of chromosome division – Cells Chromosomes replicate then plasma membrane grows inwards Creates two identical daugther cells Happens in Bacteria have a single chromosome (versus the 46 human have).

35. Budding • Some cells split resulting in mother and daughter cells • Offspring is smaller than mother • The buds grow into fully matured individuals which eventually break away from the parent organism.

36. Fragmentation • http://www.teachersdomain.org/resource/tdc02.sci.life.repro.asexual/ • In this form, the body of the parent breaks into distinct pieces, each of which can produce an offspring.

37. Regeneration • In this form, if a piece of a parent is detached, it can grow back!

38. Grafting • Used to propagate a desired variety of tree or shrub. • Involves taking a twig (scion) from a mature plant and inserting it into a cut stump (the stock). • Check it out

39. Vegetative Reproduction • Method used by plants by sending a runner (underground stems) to reproduce. • A new plant will grow at end of each runner • Some plants use other underground stems called rhizoids, bulbs, or tubers to reproduce asexually.

40. Spore Production • Some fungi and plant species release cells called spores • Spores reproduce new organisms via mitosis • Spores can be carried by water, wind or animals. • Video

41. Offspring are clones, no differences and if mutation occurs.. Uh oh! Too many individuals may fight with each other to survive Entire colonies can be wiped out if not adapted to environment Large number of offspring produced quickly Large colonies can form Large numbers or organisms may survive No energy is required to find a mate Asexual Reproduction Advantages Disadvantages

42. Use notes and handout to answer questions Work in partners Asexual Reproduction Questions

43. Read pages 176-77 What is the difference between reproductive (DNA) and theraputic cloning (stem cells)? Do you have a problem with either? Make notes for a discussion…. Do you find them morally wrong? Cloning Assignment

44. Reproductive CloningDuplicate existing organism by removing nucleus of egg cell and fusing with mammary gland cells

45. Theraputic CloningEmbryonic Stem cells grown into desired organs

46. Genetic information from two parents passed on to offspring Both parents make special cells called gametes Gametes contain only one set of chromosomes (sperm and egg) When two gametes come together (ask your parents) this is called fertilization and form a new cell called a Zygote A zygote will mature and undergo mitosis to become an embryo. What is Sexual Reproduction?

48. Diploid (Di = two) Every cell in body except gametes (sperm/egg) Contain 2n or two sets of chromosomes 2 sets of 23 = 46 chromosomes Haploid Gametes (sperm and egg) Contain n or one set of chromosome 23 chromosomes Diploid vs. Haploid

49. How do cells become Haploid? • Meiosis….

50. Meiosis – key differences from mitosis • Meiosis reduces the number of chromosomes by half. • Daughter cellsdiffer from parent, and each other. • Meiosis involves two divisions, Mitosis only one • End product is 4 haploid cells (1n) instead of 2 diploid cells (2n) • Occurs only in sex cells to produce gametes (sperm and egg)