1. Cell Reproduction

2. Starting at the beginning…
Biologically speaking, where did YOU come from?

3. Cells How many cells make up a human body?
Did you have the same number last year? What about when you were 2 years old? 2 months old?

4. Cells
Your body is made up of between 10 and 100 trillion cells. (100,000,000,000,000)
One-thousandth of them die every day

5. Cells
Where do all these cells come from?

6. Cell Reproduction

7. Cell Specialization Different body cells perform different functions
Examples: skin, nerve, red blood cells, liver cells, platelets

8. Cell Specialization
Different cells live for different amounts of time

9. Cellular Reproduction
New cells are made from copies of old cells
This process began occurring before you were born and will continue until after you die

10. Types of Cellular Reproduction
MITOSIS – results in two identical cells; used for the majority of cells in the body
MEIOSIS – results in four cells that are different from the “parents”; used for sex cells only

11. Mitosis Results in body growth or body repair
Two new cells are called “daughter cells”

12. A Review of Cell Features
Cell Membrane
Cytoplasm
Nucleus
Nuclear Membrane
Chromosomes – strands that carry a cell’s DNA
Centrioles – strong, barrell-shaped organelle

13. Mitosis
Goals – duplicate chromosomes and move them to two new daughter cells

14. Before Mitosis Begins (interphase)
Chromosomes are duplicated within the cells (exact copies)
Held together at center
Two strands are called “sister chromatids”

15. Mitosis Step 1: PROPHASE Sister chromatids thicken
Nuclear membrane breaks down
Two centrioles move apart
Fibers (strands of protein) form between centrioles

17. Mitosis Step 2: METAPHASE Centrioles to opposite ends of cell
Fibers stretch between
Sister chromatids attach to fibers
Sister chromatids line up at center of the cell

19. Mitosis Step 3: ANAPHASE Sister chromatids pulled apart from partner
Fibers pull chromatids towards centrioles at opposite ends of the cell

21. Mitosis STEP 4: TELOPHASE
Each side now has complete set of chromosomes
Fibers disappear
Nuclear membrane re-forms
Cell membrane pinches inwards to form 2 cells

23. Cytokinesis Cytokinesis
Division of the cytoplasm (cytokinesis) is complete. The two daughter cells are now separate cells in their own right.
Cytokinesis

24. Mitosis in Plant Cells 2 Differences No centrioles
Cell wall must re-form between new cells

26. How to remember order of phases?
In Patiki, Men Are Tough. Stages of mitosis/meiosis including interphase as a phase! Interphase, Prophase, Metaphase, Anaphase, Telophase.

27. Importance of Chromosomes
All chromosomes come in pairs
Humans have 23 pairs, so a normal cell has 46 chromosomes
All cells need a full set to function properly (except sex cells)

28. Chromosome Number
Before mitosis begins, cells have two of each chromosome (2N)
After chromosomes duplicate, cells have four of each chromosome (4N)
After mitosis, cells have two of each chromosome (2N)

29. Meiosis

30. Meiosis Process that creates gametes (eggs and sperm)
Cells divide twice

31. Chromosome Number Cells start with two of each chromosome (2N)
Chromosomes double (4N)
Pairs divide (2N)
Sister chromatids divide (N)

32. Importance of Meiosis
During fertilization, sperm (N) and egg (N) fuse to create one cell (2N)
New cell has complete set of chromosomes (half from mother, half from father)

33. Chromosome Number N represents number of PAIRS of chromosomes
2N = total number of chromosomes in a normal cell
N – total number of chromosomes in a gamete (sex cell)

34. Steps of Meiosis Step 1 PROPHASE I Sister chromatids thicken
Nuclear membrane breaks down
Two centrioles move apart
Fibers (strands of protein) form between centrioles

35. Steps of Meiosis Step 2: METAPHASE I
Centrioles to opposite ends of cell
Fibers stretch between
Sister chromatids attach to fibers
Sister chromatids line up at center of the cell

36. Steps of Meiosis Step 3: ANAPHASE I TELEPHASE I
Sister chromatids DO NOT separate.
TELEPHASE I

37. Steps of Meiosis Step 4: PROPHASE II Cell has been split in two
No nuclear membrane forms

38. Steps of Meiosis
Step 5:
Occurs in both cells
METAPHASE II

39. Steps of Meiosis
Step 6:
ANAPHASE II
TELEPHASE II

40. THE MOST IMPORTANT DIFFERENCE
In the first cell division, CHROMOSOME PAIRS are pulled apart.
In the second cell division, SISTER CHROMATIDS are pulled apart.

41. Meiosis
Meiosis: the division of a diploid nucleus to form four haploid genetically different daughter nuclei.
Role of Meiosis
• Increases genetic variation in the population – role in evolution
• Makes sexual reproduction possible
• Gamete formation in animals, fungi, protoctista e.g. Man
Site of Meiosis
Animals
• testis - forming sperm, the haploid male gametes;
• ovary - forming egg cells, the haploid female gametes.
Flowering plants:
• anther of the stamen - forming the haploid male spores (microspores),
• ovule of ovary - forming the haploid female spores (megaspores).

42. Cancer and Aging

43. Cancer/Aging
How are cancer and aging similar?

44. Cancer/Aging
Changes in rates of mitosis

45. Aging What properties of a person’s body change as they age?
Physically? Physiologically?

46. Cancer
Rapid, abnormal, uncontrolled mitosis
What causes cancer?

47. Cancer Causes
Viruses
Chemicals
Radiation