1. Chapter 8: Cell Reproduction
Section 1: Chromosomes
Section 2: Cell Division
Section 3: Meiosis

2. What are chromosomes?
Rod shaped structures inside the nucleus of Eukaryotic cells
Made of DNA and proteins
Contain the genes that make you, you!
Shape of the chromosome is maintained by histones

4. Chromosome Structure 3 forms of a chromosome Chromatin – ball of yarn
Chromatid – half of an x, sometimes bent
Chromosome – X
Center of X is called a centromere

5. Chromosome Types Sex Chromosomes Autosomes
Determine the sex of the organism
Males XY
Females XX
2 out of 46 in the human cell
Autosomes
All the other chromosomes
44 out of 46 in the human cell

6. Sex Chromosomes and Autosomes
Section 1 Chromosomes
Chapter 8
Sex Chromosomes and Autosomes
Click below to watch the Visual Concept.
Visual Concept

7. What are Homologous Chromosomes?
Also called homologues
2 copies of the chromosome
One from Mom; One from Dad
Have the same size
Have the same shape
Have the same information (genes)

8. Two Types of Cells Diploid Haploid
Cells that have chromosomes in pairs
Symbol 2n
Somatic cells or body cells are like this
Humans diploid number is 46.
Haploid
Cells that do not have chromosomes in pairs
Symbol 1n
Gametes are like this
Sex cells
Sperm and egg cells
Humans haploid number is 23.

9. Cell Division in Prokaryotes, continued
Section 2 Cell Division
Chapter 8
Cell Division in Prokaryotes, continued
Binary fission is the process of cell division in prokaryotes.

10. Section 2

11. Two types of Reproduction
Asexual Reproduction
Production of offspring from one parent
Mitosis
Sexual Reproduction
Production of offspring from 2 parents
Meiosis

12. How do little elephants grow up to be BIG elephants?

13. Why do animals shed their skin?

14. The process of asexual reproduction begins after a sperm fertilizes an egg.

15. Three reasons why cells reproduce by asexual reproduction: 1. Growth 2
Three reasons why cells reproduce by asexual reproduction: Growth Repair Replacement
Skin cancer - the abnormal growth of skin cells - most often develops on skin exposed to the sun.
Cell that reproduce by asexual reproduction reproduce constantly.

16. Animated Mitosis Cycle
Interphase
Prophase
Metaphase
Anaphase
Telophase & Cytokinesis

17. Interphase occurs before mitosis begins
3 phases
G1 – cell is growing
S – DNA is being copied
G2 – cell is preparing for mitosis
Nuclear Membrane
And nucleolus are visible
CHROMATIN!
CELL MEMBRANE
Nucleus
Cytoplasm

18. Interphase Plant Cell Animal Cell
Photographs from:

19. Prophase 1st step in Mitosis
Nuclear membrane & nucleolus disappear by end of prophase
Mitosis begins (cell begins to divide)
Chromosomes are visible
Centrioles (or poles) appear and begin to move to opposite end of the cell.
Spindle fibers form between the poles.
Centrioles
Sister chromatids
Spindle fibers

20. Prophase Plant Cell Animal Cell Spindle fibers Centrioles
Photographs from:

21. Metaphase 2nd step in Mitosis
Chromosomes attach to the spindle fibers at the centromere
CHROMOSOME
Centrioles
Spindle fibers

22. Metaphase Plant Cell Animal Cell
Photographs from:

23. Anaphase 3rd step in Mitosis
Chromatids (or pairs of chromosomes) separate and begin to move to opposite ends of the cell.
Centrioles
Spindle fibers

24. Anaphase Plant Cell Animal Cell
Photographs from:

25. Telophase 4th step in Mitosis
Nuclear membrane & nucleolus are visible by end of telophase
Two new nuclei form.
Chromosomes appear as chromatin (threads rather than rods).
Mitosis ends.
Overlaps with cytokinesis!
Nuclei
Nuclei
Chromatin

26. Telophase Plant Cell Animal Cell
Photographs from:

27. Cytokinesis occurs after mitosis
Division of the cytoplasm
Cell membrane moves inward to create two daughter cells – each with its own nucleus with identical chromosomes.
Animal cells – form a cleavage furrow
Plant cells – form a cell plate, which becomes the cell wall.

29. Animal Mitosis -- Review
Interphase                                                             
Prophase                                                             
Metaphase                                                             
Anaphase                                                             
Telophase                                                             

30. Plant Mitosis -- Review
Interphase                                                             
Prophase                                                             
Metaphase                                                             
Anaphase                                                             
Telophase                                                             

31. IPMATC REMEMBER! Interphase Prophase Metaphase Anaphase Telophase
Cytokinesis
IPMATC
A mnemonic to help remember the stages of mitosis.
I Pray More At The Church

32. Cell Cycle

34. Mitosis Animation

35. Control of Cell Division
Section 2 Cell Division
Chapter 8
Control of Cell Division
Cell division in eukaryotes is controlled by many proteins.
Control occurs at three main checkpoints.
G1 checkpoint – check to see whether the cell is healthy and is large enough to divide
G2 checkpoint – check to make sure DNA is copied correctly
Mitosis checkpoint – if cell divided correctly, then signals are made to exit mitosis

36. Control of the Cell Cycle
Section 2 Cell Division
Chapter 8
Control of the Cell Cycle
Click below to watch the Visual Concept.
Visual Concept

37. Control of Cell Division, continued
Section 2 Cell Division
Chapter 8
Control of Cell Division, continued
When Control is Lost: Cancer
Cancer is uncontrolled growth of cells
Cancer may result if cells do not respond to control mechanisms.
Can be caused by mutations in DNA

38. Formation of Haploid Cells
Section 3 Meiosis
Chapter 8
Formation of Haploid Cells
Meiosis is a process of nuclear division that reduces the number of chromosomes in new cells to half the number in the original cell.
Start with 46 and end with 23
Meiosis leads to four haploid cells (gametes) rather than two diploid cells as in mitosis.
Done by germ cells
Meiosis produces haploid gametes.
Is considered sexual reproduction
Creates genetic diversity
Two divisions

39. Section 3 Meiosis
Chapter 8
Meiosis I
Meiosis I includes prophase I, metaphase I, anaphase I, and telophase I.
Crossing-over, which is when portions of homologous chromosomes exchange genetics material, occurs during prophase I and results in genetic recombination.

40. Prophase I Homologous chromosomes (paired chromosomes) become visible
Nuclear membrane and nucleolus disappear
Spindle fiber starts to appear
Crossing over occurs – portions of the chromatid break off and attach to other homologous chromosome

41. Tetrads and Crossing-over of Genetic Material
Section 3 Meiosis
Chapter 8
Tetrads and Crossing-over of Genetic Material
Click below to watch the Visual Concept.
Visual Concept

42. Metaphase 1
Homologous chromosomes (tetrads) line up at the equator and connect to spindle fibers at their centromeres

43. Anaphase 1
Homologous chromosomes split and individual chromosomes move to poles
They assort independently of one another- independent assortment

44. Telophase 1and Cytokinesis 1
There are 2 new cells at this point
Each new cell has half the number of chromosomes as the parent germ cell
So they are now haploid

45. Meiosis 2 Has prophase II, metaphase II, anaphase II and telophase II
Exactly like mitosis
Four new haploid cells result
Four gametes
Depends on whether it is an animal or a plant cell

46. Section 3 Meiosis
Chapter 8

47. Gametogenesis – making of gametes
Spermatogenesis
Making of sperm cells
Meiosis will result in 4 mature sperm cells or spermatozoa
Oogenesis
Making of mature egg cells, or ova
Meiosis will result in 1 mature egg cell and 3 polar bodies that die