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Genetic Control of Protein Synthesis, Cell Function, and Cell Reproduction

Genetic Control of Protein Synthesis, Cell Function, and Cell Reproduction. PART 2. Cell Reproduction. Mitosis is cell division Growth Cell repair Not meiosis Goal is to make identical cells Cells do not divide all the time. Mitosis is a very short period Most of the time is Interphase.

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Genetic Control of Protein Synthesis, Cell Function, and Cell Reproduction

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  1. Genetic Control of ProteinSynthesis, Cell Function,and Cell Reproduction PART 2

  2. Cell Reproduction Mitosis is cell division • Growth • Cell repair • Not meiosis • Goal is to make identical cells • Cells do not divide all the time

  3. Mitosis is a very short period • Most of the time is Interphase

  4. M(mitosis) G2(Gap 2) G1(Gap 1) EUKARYOTIC CELL CYCLE Cells that cease division S phase(DNA synthesis) Genetic Control of Cell Reproduction Life Cycle of the Cell: M phase: • mitosis • cytokinesis Interphase (>95%): • G1 phase • S phase (DNA synthesis) • G2 phase

  5. DNA Replication: S phase • switched on by the cytoplasmic S-phase activator • Replication is initiated at replication origin and proceeds in both directions. • Entire genome is replicated once - further replication is blocked • involves DNA polymerase and other proteins that function to unwind and stabilize the DNA and “prime” DNA replication of the “lagging” strand.

  6. DNA Replication: S phase • nucleotides are always added to the 3’ end (DNA and RNA) • formation of Okazaki fragments on lagging strand • “new” DNA is proofread by DNA polymerase • repairs are made and gaps filled by DNA ligase

  7. Chromosomes and Their Replication • “New” DNA helices associate with histones to form chromosomes • The two chromosomes remain temporarily attached at the centromere. • Together, these chromosomes are called chromatids.

  8. Mitosis • Remember PMAT • Prophase • Metaphase • Anaphase • Telophase

  9. Interphase • Technically not part of mitosis • DNA is copied (duplicated) • Centrosomes are duplicated

  10. Prophase • Chromosomes thicken

  11. Metaphase • For middle

  12. Anaphase • ”away” • Chromosomes move to opposite side of the cell • They have spindles

  13. Telophase • For two

  14. Stages of Cell Reproduction Mitosis: M phase 1. Assembly of the mitotic apparatus 2. Prophase (A,B,C) 3. Prometaphase (D) 4. Metaphase (E) 5. Anaphase (F) 6. Telophase (G, H) Figure 3-13

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  16. Cell Differentiation Different from reproduction ... • changes in physical and functional properties of cells as they proliferate • results not from the loss of genes but from the selective repression/expression of specific genes • development occurs in large part as a result of “inductions,” one part of the body affecting another

  17. The cell cycle & cancer • Growing of cells out of control

  18. Cancer Dysregulation of cell growth Caused in all or almost all cases by the mutation or abnormal activation of genes that encode proteins that control cell growth and/or mitosis • Proto-oncogenes: the “normal” genes • Oncogenes: the “abnormal” gene • Antioncogenes: genes whose product suppress the activation of oncogenes Not all mutations lead to cancer!

  19. What causes these mutations? • Ionizing radiation: disrupts DNA strands • Chemicals: “carcinogens” • Physical irritants: e.g., abrasion of the intestinal lining • Hereditary “tendencies”: e.g., some breast cancer • Viruses: so-called “tumor viruses” (particularly retroviruses)

  20. Q: Why does cancer kill? A: Cancer cells compete successfully with normal cells for limited nutrients

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