1. Mitosis and DNA Replication

2. Cell Division
Occurs in humans and other organisms at different times in their life.
Cell Division differs depending on type of organism:
Eukaryotic organisms undergoing growth, development, repair, or asexual reproduction divide by mitosis.
EXAMPLE: new hair, nails, skin, liver, cells, etc… are produced.

3. Interphase
95% of cell cycle in interphase
Cells replicate their DNA

4. Mitosis
Mechanism used by cells to replicate DNA and produce identical cell copies.
5% of cell cycle is mitosis
Happens in all cells

5. Mitosis It is broken down into 5 major stages: Prophase Metaphase
Anaphase
Telophase

6. Prophase 1st phase of Mitosis
Nucleolus breaks down & Nuclear membrane disappears
Chromosomes condense –sister chromatids stay attached by the centromere
Kinetochore fibers form

7. Metaphase 2nd phase of Mitosis
The kinetochore fibers move the Chromosomes to the equator (middle)
Each chromatid is attached to the fibers at the centromere.

8. Anaphase 3rd phase of Mitosis Centromeres split
Sister chromatids are pulled apart to opposite poles of the cell
After chromatids separate, they are considered to be individual chromosomes.

9. Telophase 4th phase of Mitosis
Chromosomes begin to uncoil back into chromatin state.
Cytokinesis
Cytoplasm divides
Two new daughter cells are now separate
2 nuclear membranes form around each set of chromosomes.
Nucleolus forms in
each of the newly
formed cells.

10. Mitosis Animation

11. Deoxyribose Nucleic Acid
DNA
double-stranded
sugar = deoxyribose
bases = A,T,C,G

12. Free Nucleotide

13. DNA Replication

14. DNA Replication
DNA copies itself exactly
(Occurs within the nucleus)
Any mistake in copying = mutation

15. Basic Facts of DNA Replication
Complementary base pairing
makes replication possible
C - G
A - T

16. Basic Facts of DNA Replication
One side of DNA molecule is a
template for making the other side (strand)

17. DNA Replication Step 1: Uncoil & unzip DNA molecule
This occurs because of a weak hydrogen bond between the bases.

18. DNA Replication
Step 2:
Enzyme brings in complementary N-bases

19. DNA Replication Each new DNA molecule contains one old strand &
one new strand

20. DNA Replication Animation

21. The Cell Cycle and Cancer

22. Cancer: Why does it exist?

23. There are several factors that regulate the cell cycle and assure a cell divides correctly.
1.Before a cell divides, the DNA is checked to make sure it has replicated correctly. (If DNA does not copy itself correctly, a gene mutation occurs.
DNA replication animation:click on DNA picture

24. 2. Chemical Signals tell a cell when to start and stop dividing.
(Target cells animation: click on go sign)

25. 3. Neighboring cells communicate with dividing cells to regulate their growth also.
(Normal contact inhibition animation: click on petri dish)

26. Cancer is a disease of the cell cycle
Cancer is a disease of the cell cycle. Some of the body’s cells divide uncontrollably and tumors form.
Tumors in Liver
Tumor in Colon

27. DNA mutations disrupt the cell cycle.
Mutations may be caused by:
1. radiation
2. smoking
3. Pollutants
4. chemicals
5. viruses

28. While normal cells will stop dividing if there is a mutation in the DNA, cancer cells will continue to divide with mutation.

29. Due to DNA mutations, cancer cells ignore the chemical signals that start and stop the cell cycle.
2 animations of cancer cells dividing: click on picture

30. Due to DNA mutations, cancer cells cannot communicate with neighboring cells. Cells continue to grow and form tumors.
Skin cancer
(cancer cells dividing: click on picture.)

31. SUMMARY Normal Cell Division DNA is replicated properly.
2. Chemical signals start and stop the cell cycle.
3. Cells communicate with each other so they don’t become overcrowded.
Cancer Cells
Mutations occur in the DNA when it is replicated.
2. Chemical signals that start and stop the cell cycle are ignored.
3. Cells do not communicate with each other and tumors form.

32. Cancer Terminology
Cancer – a large group of diseases characterized by the uncontrolled growth and spread of abnormal cells
Neoplasm – new growth of tissue that serves no physiological function
Tumor – clumping of neoplasmic cells
Malignant - cancerous
Benign - noncancerous
Biopsy – microscopic examination of cell development

33. Cancer Terminology
Metastasis – malignant tumors that are not enclosed in a protective capsule have the ability to spread to other organs
Mutant cells – disruption of RNA and DNA within normal cells may produce cells that differ in form, quality and function from the normal cell

35. Factors Believed to Contribute to Global Causes of Cancer
Figure 16.2

36. Treating Cancers
Cancer treatments include drugs that can stop cancer cells from dividing. (chemotherapy, radiation)

37. Review