Cellular Division

1. Cellular Division Chapters 6, 27, and 42-43

2. Objective 1: Structure of Chromosome • DNA is coiled around histone proteins • Appears like beads on a string • It is then coiled further around the existing coils • Also called a “supercoil”

7. Some definitions to help understand • Homologous Chromosomes- chromosomes that are similar in size, shape, and genetic information. Chromosomes are made of 2 essential parts • 1. Chromatid- 2 copies per chromosome • 2. Centromere- Protein disk that connect the two chromatids

9. Objective 2: Terms • Haploid- 1 set of chromosomes, 23 chromosomes per cell (egg or sperm) AKA Sex cells. Symbol n • Diploid- 2 sets of chromosomes, 46 per cell, Somatic cells or body cells. Symbolized by 2n. • Gamete- Germ cell, sex cell, eggs and sperm= 23 chromosomes each. • Zygote- (Fertilized egg), sperm unites w/ egg= 46 Chromos

10. Objective 3: Cell Cycle • G1- Growth and F(x) of cells. Cell prepares for DNA Replication. (Cancer cells skip this phase). • S- Chromosome/DNA replication • G2- Organelles replicate to prepare for cell division by acquiring proper proteins. • M- (Mitosis)(Nuclear Division) Prophase, Metaphase, Anaphase, Telophase. • C- (Cytokinesis)(Cytoplasmic division) Cleavage furrow or cell plate.

11. 90% of a cell’s life is spent in G1,S, and G2 phases.

12. Objective 4: Cell Division Stages • Interphase • G1, S, G2 • Chromatin- Uncoiled, working DNA • Cell is functioning • DNA replication • Preparations for division

13. Prophase • Nuclear Membrane dissolves and breaks down. • Chromatin condenses and become visible Chromosomes. • Centrioles (hollow, barrel shaped cell structure) move to opposite poles and a network of spindle fibers form.

14. Metaphase • Paired chromosomes (Chromatids) line up in the middle (equatorial plane). • Spindles attached to each chromosome at centromere, which are already connected to the centrioles.

15. Anaphase • Centromere divides and chromosomes physically split • Spindle fibers contract and shorten, pulling the chromosome to the opposite poles. • Mirror images- Equatorial division

16. Telophase • Chromosomes arrive at opposite poles and spindles disappear. • Nuclear envelope reforms • Chromosomes uncoil to become working chromatin again • Cytokinesis begins • Plants= Cell wall • Animals= Cleavage furrow

21. Video of Mitosis

22. Objective 5: Cancer Causes: • 4 Theories • All result in mutations that cause oncogenes to be turned on and tumor suppressor genes to be turned off. • This messes up your DNA. • Oncogenes- Stimulate growth AKA Cell division. • Tumor suppressor genes- restrain cells’ ability to divide.

23. 4 Theories • Standard - result in mutations that cause oncogenes to be turned on and tumor suppressor genesto be turned off • Modified – something disables the repairing of DNA leading to mutations • Early instability – “master genes” silenced that leads to mutations • Aneuploidy – too many or too few genes that leads to mutations

24. Molecular Biology • Oncogenes and tumor suppressor genes are both types of transcription factor genes, (homeoticgenes). • Transcription factors turn on or turn off lots of other genes. • Think of them as traffic lights, (oncogenes) and gates, (tumor suppressor genes)

26. Development of Cancer • Initiation- a mutation occurs to usually 1 (or more) genes. Lag time to next stage= 20-25 years. • Promotion- Anything that happens that leads to expression of the mutation. Such as cells dividing too quickly. • Progression- tumor grows larger and larger, tumor produces enzymes and polypeptides that direct blood to tumor.

27. Cancer Characteristics 6 common characteristics to all deadly cancers • Growth w/out a go signal • Growth even against stop signals • Evades autodestruct signals • Ability to stimulate blood vessel construction • Immortality • Metastasis- Ability to spread to new tissue.

28. Cancer Treatments • Many are specific to a particular type of cancer. Others can work on a number of cancer types. Most treatments try to work by killing cancerous cells. Common Treatments: • Radiation- malignant tumors • Chemotherapy- Kills cells that rapidly divide • Surgery- Removing the tumor

29. Treatment continued… Benefits: Kill cancer cells. -RNAi – siRNA Turn off Oncogenes -Potentially Perfect Cure Drawbacks: Illness Radiation- can’t pinpoint cancer cells. Chemo- targets all dividing cells. Surgery- may not get all cells. How can cancer kill you? Handout

30. Objective 7: Meiosis Stages: Meiosis: I, P, M, A,T M= Crossing Over Meiosis II: P, M, A, T Overview of Meiosis I and Meiosis II Meiosis I: Homologous chromosomes separate into 2 diploid cells. Similar to Mitosis. Meiosis II: 2 diploids become 4 haploid cells.

33. Purpose of Meiosis • Production of gametes or sex cells (eggs and sperm) • Each 1 contains the haploid number of chromosomes

34. Importance of Meiosis • The offspring have the correct diploid chromosome number • Sex provides for combination of genes= better survival • AKA: Genetic Recombination

35. Objective 8: Mitosis vs. Meiosis Mitosis Meiosis • 1 cell -> 2 cells • Maintain chromosome # • Diploid • Produce body cells • Identical cells • 1 cell -> 4 sperms 1 egg (3 polar bodies) • Reduce chromosome # • Haploid • Produce sex cells • Cells are different

37. Objective 9: Sexual vs. Asexual Sexual Asexual • Advantages • Diversity • Genetic recombination • Disadvantages • Few offspring • Energetically unfavorable • Advantages • Tons of offspring • Don’t need anybody else • Disadvantages • No diversity= little evolution • Limited Environment

38. Objective 10: Evolutionary developments • Multicellular • Tissues • Bilateral Symmetry • Body Cavity • Coelom • Segmentation • Jointed Appendages • Deuterostomes • Notochord

39. MULTICELLULARITY cell specialization

40. Tissues – Further Specialization

41. Bilateral Symmetry- Centralized Sense Receptors

42. Body cavity and Coelom – Room to grow complex organ systems.

44. Segmentation- More Specialization, mostly organs

45. Segmentation

46. Jointed Appendages- Better Mobility

47. Deuterostomes- Blastopore forms Anus

48. Notochord- Backbone

49. Objective 11: Embryonic development 1st Trimester (1-3 months) • Week 1: Cleavage- Results in a hollow ball of calls called a blastocyst • Week 2: Gastrulation- Formation of the 3 primary tissues - Endoderm, Mesoderm, Ectoderm • Week 3: Neurulation- Formation of hollow dorsal nerve tube. - Blood vessels begin to form • Week 4: Organogenesis- Body Organs forms - The heart begins to beat and limb buds form.