1. The Cellular Basis of Inheritance

2. Cells divide in order to: Repair damage To grow To produce offspring
Why do we need new cells?
Cells divide in order to:
Repair damage
To grow
To produce offspring

3. Repair and Growth

4. Reproduction
Asexual: process in which a single cell or set of cells produces offspring that inherit all their genetic material from one parent
Sexual: process in which genetic material from two parents combines and produces offspring that differ genetically from either parent

5. Chromosomes and Cell Division
Almost all the genes of a eukaryotic cell are located in the cell nucleus.
Most of the time, this genetic material exists as a mass of very long fibers that are too thin to be seen under a light microscope.

6. The long, thin fibers are called Chromatin
Chromatin consists of DNA wound around proteins molecules called histones

7. Chromatin Next the DNA is wrapped into a tight helical formation
When a cell prepares to divide these fibers condense and become visible under the microscope and are called CHROMOSOMES

9. Chromosomes
When a cell is preparing to divide, chromatin condense into chromosomes
The human somatic cell (body cell) has 46 chromosomes = diploid
An egg and sperm cell only has 23 = haploid
Each chromosome may contain thousands of genes

10. Chromosomes
Before a cell divides, it replicates all of its chromosomes
Each chromosome now consists of 2 identical joined copies called sister chromatids
Each sister chromatid is joined by a centromere

11. Chromosome
Called Sister Chromatids

12. Picture of all the Chromosomes in a human cell (Karyotype)

13. The Cell Cycle Describes the process of cell division
Begins with interphase, followed by mitosis and cytokinesis

14. Cell Cycle and Mitosis
The eukaryotic cell cycle is divided into two major phases: interphase and cell division.

15. A. Interphase
Ninety percent or more of the cell cycle is spent in interphase. During interphase, cellular organelles double in number, the DNA replicates, and protein synthesis occurs. The chromosomes are not visible and the DNA appears as uncoiled chromatin

16. Interphase is divided into the following stages:

17. G1 phase
During G1 phase, the cell grows and differentiates.
New organelles are made but the chromosomes have not yet replicated.

18. S phase
DNA synthesis occurs during S phase.
The chromosomes replicate in preparation for cell division

19. G2 phase
During G2 phase, molecules that will be required for cell replication are synthesized.

20. Cell Division
Cell division consists of nuclear division and cytoplasmic division. Nuclear division is referred to as mitosis while cytoplasmic division is called cytokenesis

21. Interphase in a plant cell:
Interphase in an animal cell

22. Mitosis (nuclear division)
Mitosis is the nuclear division process in eukaryotic cells and ensures that each daughter cell receives the same number of chromosomes as the original parent cell. Mitosis can be divided into the following phases: prophase, metaphase, anaphase, and telophase.

23. Prophase
During prophase, the chromatin condenses and the chromosomes become visible. Also the nucleolus disappears, the nuclear membrane fragments, and the spindle appartus forms and attaches to the centromeres of the chromosomes.

24. Prophase
Prophase in a plant cell
Prophase in an animal cell

25. Metaphase
During metaphase, the nuclear membrane fragmention is complete and the duplicated chromosomes line up along the cell's equator.

26. Metaphase
Metaphase in a plant cell
Metaphase in an animal cell:

27. Anaphase
During anaphase, diploid sets of daughter chromosomes separate and are pushed and pulled toward opposite poles of the cell. This is accomplished by the polymerization and depolymerization of the microtubules that help to form the spindle apparatus.

28. Anaphase
Anaphase in a plant cell:
Anaphase in an animal cell

29. Telophase
During telophase, the nuclear membrane and nucleoli reform, cytokinesis is nearly complete, and the chromosomes eventually uncoil to chromatin. Usually cytokinesis occurs during telophase.

30. Telophase
Telophase in a plant cell
Telophase in an animal cell

31. Cytokinesis (cytoplasmic division)
During cytokinesis, the dividing cell separates into two diploid daughter cells..

32. Cytokinesis (cytoplasmic division)
In animal cells, which lack a cell wall and are surrounded only by a cytoplasmic membrane, microfilaments of actin and myosin attached to the membrane form constricting rings around the central portion of the dividing cell and eventually divide the cytoplasm into two daughter cells

33. Cytokinesis (cytoplasmic division)
In the case of plant cells , which are surrounded by a cell wall in addition to the cytoplasmic membrane, carbohydrate-filled vesicles accumulate and fuse along the equator of the cell forming a cell plate that separates the cytoplasm into two daughter cells.

34. Cytokinesis in plants vs. animal cells
In animal cells, cytokinesis begins in anaphase and continues until the cytoplasm has completely divided equally.
Indentation is caused by the contraction of microfilaments just under the plasma membrane

35. In plant cells, a disk containing cell wall material called a cell plate forms inside the cell and grows outward
Eventually the cell wall divides into 2

36. 2 diploid cells are produced Somatic body cells
Mitosis
2 diploid cells are produced
Somatic body cells
Genetically identical cells produced

37. Cancer
Caused by uncontrolled cell reproduction (mitosis) and severe disruption of the mechanisms that control mitosis
These cells form a mass called a tumor
Benign tumor: abnormal mass of normal cells

38. Malignant tumor: abnormal mass of cancer cells
Malignant tumor displaces the normal tissue as it grows
If it is not removed, the cells can break off and spread to other areas of the body via blood or lymph
The spread of cancer cells beyond their original site is called metastasis

39. The Cell Cycle and Cancer

40. 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.

41. 2. Chemical Signals tell a cell when to start and stop dividing.

42. Neighboring cells communicate with dividing cells to regulate their growth also.

43. 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

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

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

46. Due to DNA mutations, cancer cells ignore the chemical signals that start and stop the cell cycle.

47. Due to DNA mutations, cancer cells cannot communicate with neighboring cells. Cells continue to grow and form tumors.
Skin cancer

48. 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.

49. Treating Cancers
Cancer treatments include drugs that can stop cancer cells from dividing.

50. Karyotype Typical human cell has 46 chromosomes
A display of the all 46 chromosomes is called a karyotype
Each person has 2 twin chromosomes called homologous chromosomes
Where do you think each came from?

52. Homologous chromosomes
Each homologous chromosome carries the same sequence of genes controlling a characteristic, but different versions
Example:
Eye color is located on the same place, but may be different versions (blue, brown, hazel)
Different from sister chromatids because the material is genetically different

53. Humans have 23 homologous pairs of chromosomes
The 23rd pair are called sex chromosomes
All chromosomes look the same except for the sex csomes
Males have XY
Females have XX

54. Meiosis
Sexual reproduction that involves formation of sex cells (Chromosome 23)
4 haploid cells are produced
Sex cells (gametes)
All 4 cells genetically different