1. Genetic Control of Protein Synthesis, 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. Cells that cease division S phase (DNA synthesis)
Genetic Control of Cell Reproduction
Life Cycle of the Cell:
M phase:
mitosis
cytokinesis
Cells that cease division
M (mitosis)
G1 (Gap 1)
G2 (Gap 2)
S phase (DNA synthesis)
EUKARYOTIC CELL CYCLE
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. DNA Repair, “Proofreading,” and “Mutations”
Following replication and prior to mitosis, DNA polymerase “proofreads” the “new” DNA, and cuts out mismatches
DNA ligase replaces the mismatches with complementary nucleotides
A “mistake” during transcription results in a mutation causing the formation of an abnormal protein
Approximately 10 DNA mutations are passed to the next generation, however two copies of each chromosome almost always ensures the presence of a functional gene

8. 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.

9. Mitosis
Remember PMAT
Prophase
Metaphase
Anaphase
Telophase

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

11. Prophase Chromosomes thicken Microtubules – mitotic spindle forming
Nuclear envelope is fragmenting (prometaphase)
Microtubules are attaching to kinetochore

12. Metaphase
For middle
They line up in the middle, lining up in the metaphase plate

13. Anaphase ”away” Chromosomes move to opposite side of the cell
They have spindles
Chromatids separate
Equal numbers of DNA in each of the daughter cells

14. Telophase For two Telophase & cytokinesis Cell elongation
Cleavage furrrow
Daughter nuclei form

15. 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

16. FILM

17. 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

18. The cell cycle & cancer
Growing of cells out of control

19. Not all mutations lead to 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!

20. 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)

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