1. Chapter 8 Objectives Section 1 Chromosomes
Describe the structure of a chromosome.
Identify the differences in structure between prokaryotic chromosomes and eukaryotic chromosomes.
Compare the numbers of chromosomes in different species.
Explain the differences between sex chromosomes and autosomes.
Distinguish between diploid and haploid cells.

2. Chapter 8 Chromosome Structure
Section 1 Chromosomes
Chapter 8
Chromosome Structure
Chromosomes are rod-shaped structures made of DNA and protein.
In eukaryotes, DNA wraps around proteins called histones to help maintain the compact structure of chromosomes.
This allows the DNA to fit within the cell

3. Chapter 8 Chromosome Structure Figure 8-1 Page 151
Section 1 Chromosomes
Chapter 8
Figure 8-1 Page 151
Chromosome Structure
As a cell prepares to divide, its DNA coils around histones and twists into rod-shaped chromosomes

4. Chromosome Structure, continued
Section 1 Chromosomes
Chapter 8
Chromosome Structure, continued
Open books to page 152, figure 8-2
Chromatids are duplicate halves of a chromosome
The point at which both chromatids are attached is called the centromere (like the point where an X comes together)

5. Chromosome Structure, continued
Section 1 Chromosomes
Chapter 8
Chromosome Structure, continued
Comparing chromosome structure of prokaryotes and eukaryotes
Prokaryotes (bacteria)
Eukaryotes (plants and animals)
simple
complex
circular
linear
attached to cell membrane
found free in nucleus
one
many

6. Chromosome Numbers of Various Organisms
Section 1 Chromosomes
Chapter 8
Chromosome Numbers of Various Organisms
Each species has a characteristic number of chromosomes in each cell.
Similar to Table 8-1 on page 152

7. Chromosome Numbers, continued
Section 1 Chromosomes
Chapter 8
Chromosome Numbers, continued
Sex Chromosomes and Autosomes
Sex chromosomes are chromosomes that determine the sex of an organism.
In humans, sex chromosomes are either X or Y
Females XX
Males XY
All of the other chromosomes
in an organism are autosomes.

8. Chromosome Numbers, continued
Section 1 Chromosomes
Chapter 8
Chromosome Numbers, continued
Breakdown of Human chromosomes
46 chromosomes total
2 are sex chromosomes,
44 are autosomes
Karotype is a pictomicrograph of chromosomes in a normal dividing cell found in a human
Figure 8-3 on page 153

9. Chromosome Numbers, continued
Section 1 Chromosomes
Chapter 8
Chromosome Numbers, continued 1n
Diploid cells: have two homologues of each chromosome, is designated by the symbol 2n, and has chromosomes found in pairs
Haploid cells: are the reproductive cells or Gametes (sperm and egg), have ½ the number of chromosomes that are present in diploid, and is designated by the symbol 1n 1n

10. Chromosome Numbers, continued
When gametes- a sperm cell (1n) and egg cell (1n) combine to create a new organism, the new cell will be diploid (2n).
If the reproductive cells were diploid, the new cell would have too many chromosomes and would not be functional
Gametes

11. Chapter 8 Objectives Section 2 Cell Division
Describe the events of cell division in prokaryotes.
Name the two parts of the cell that are equally divided during cell division in eukaryotes.
Summarize the events of interphase.
Describe the stages of mitosis.
Compare cytokinesis in animal cells with cytokinesis in plant cells.
Explain how cell division is controlled.

12. Cell Division in Prokaryotes
Section 2 Cell Division
Chapter 8
Cell Division in Prokaryotes
Cell division is the process by which cells reproduce themselves.
Approximately 2 trillion cells are produced by an adult human body every day

13. 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.
Remember that bacteria is considered a prokaryote…hint hint hint
Page 154 Figure 8-4

14. Cell Division in Eukaryotes
Section 2 Cell Division
Chapter 8
Cell Division in Eukaryotes
Cell Cycle
The cell cycle is the repeating set of 5 events in the life of a cell.
The cell cycle consists of cell division and interphase.
Cell division in eukaryotes includes nuclear division, called mitosis, and the division of cytoplasm, called cytokinesis.

15. Cell Division in Eukaryotes,
Section 2 Cell Division
Chapter 8
Cell Division in Eukaryotes,
Look at figure 8-5 page 155
Cell cycle starts at G1 and continues through cytokinesis
Correct sequence would be: G1-S-G2-M-C
Make sure you know what occurs at each of those stages
Interphase consists of growth (G1), DNA replication (S), and preparation for cell
division (G2).
Occupies most of the cell’s life

16. Chapter 8 Stages of Mitosis
Section 2 Cell Division
Chapter 8
Stages of Mitosis
Mitosis is divided into 4 stages: prophase, metaphase, anaphase, and telophase.
Mitosis results in two offspring cells that are genetically identical to the original cell.
Follow along, pages
Use Figure 8-6, page 156

17. “WIND UP” “MIDDLE” Chapter 8 Stages of Mitosis
Section 2 Cell Division
Chapter 8
Stages of Mitosis
Prophase – 1st phase of mitosis
chromosomes grouped
Centrosomes move towards poles of the cell and start to form spindle fibers
Metaphase – 2nd phase of mitosis
chromosomes move to center (middle)
“WIND UP”
“MIDDLE”

18. “APART” “TWO” Chapter 8 Stages of Mitosis
Section 2 Cell Division
Chapter 8
Stages of Mitosis
“APART”
Anaphase – 3rd phase of mitosis
Chromatids of each chromosome will split
Telophase – 4th phase of mitosis
Chromosomes reach opposite end of original cell
“TWO”

19. Chapter 8 Stages of Mitosis Cytokinesis – NOT a phase of mitosis
Section 2 Cell Division
Chapter 8
Stages of Mitosis
Cytokinesis – NOT a phase of mitosis
Cell splits into two cells that will be genetically identical to original cell

20. Section 2 Cell Division
Chapter 8
Cytokinesis
During cytokinesis in animal cells, a cleavage furrow pinches in and eventually separates the dividing cell into two cells.
In plant cells, a cell plate separates the dividing cell into two cells after the formation of a cell wall

21. Chapter 8 Stages of Mitosis Put these 4 illustrations in order
Section 2 Cell Division
Chapter 8
Stages of Mitosis
Put these 4 illustrations in order
Looking above, which stage are the centromeres dividing?
Which illustration above shows the starting point for mitosis?

22. Chapter 8 Stages of Mitosis Section 2 Cell Division
Put these 4 illustrations in order
3, 2, 1, 4
Looking above, which stage are the centromeres dividing?
1 (Anaphase)
Which illustration above shows the starting point for mitosis?
3 (Prophase)

23. 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: If cell is healthy and has suitable size during G1 phase, proteins will initiate DNA synthesis, if not healthy enough cell division stops
G2: DNA repair enzymes check the results of DNA replication, if passed they will allow cell to continue to steps of mitosis
Mitosis checkpoint: If the cell passes this checkpoint, proteins signal the cell to exit mitosis. The cell the enters into the G1 phase again

24. Control of Cell Division, continued
Section 2 Cell Division
Mitosis Song
Chapter 8
Control of Cell Division, continued
When Control is Lost: Cancer
Cancer may result if cells do not respond to control mechanisms. (checkpoint stops don’t work)
Cancer is the uncontrolled growth of cells (tumors)

25. Chapter 8 Objectives Section 3 Meiosis
Compare the end products of meiosis with those of mitosis.
Summarize the events of meiosis I.
Explain crossing-over and how it contributes to the production of unique individuals.
Summarize the events of meiosis II.
Compare spermatogenesis and oogenesis.
Define sexual reproduction.

26. Formation of Haploid Cells
Section 3 Meiosis
Chapter 8
Formation of Haploid Cells
Meiosis - nuclear division that reduces the number of chromosomes in new cells to half the number in the original cell.
Cells undergoing meiosis divide twice

27. Meiosis leads to four haploid cells or 1n (gametes- sex cells) rather than two diploid or 2n cells as in mitosis. 2n 2n 2n 2n 1n

28. Section 3 Meiosis
Chapter 8
Meiosis I
Meiosis I includes prophase I, metaphase I, anaphase I, and telophase I.
Make sure that you know the differences between the meiosis and mitosis phases – they do have the same names
Crossing-over- homologous chromosomes exchange genetics material and results in genetic recombination (mixing up of DNA)
Crossing-over acts as a source of variation within a species

29. -Each pair of homologue chromosomes is called a tetrad.
Section 3 Meiosis
Chapter 8
Follow along by looking at Figure 8-11 pages
Meiosis I
Prophase I:
-DNA coils into chromosomes which line up next to their homolog This pairing up is called synapsis.
-Each pair of homologue chromosomes is called a tetrad.
Metaphase I:
-Tetrads line up along the middle of the cell.

30. Chapter 8 Meiosis I Anaphase I
Section 3 Meiosis
Chapter 8
Meiosis I
Anaphase I
–Homologous chromosome moves to opposite pole of dividing cell
The random separation of homologous chromosomes is called independent assortment, which results in genetic variation
Telophase I and Cytokinesis I
– chromosomes reach opposite end cytokinesis begins,
New cells contain haploid number of chromosomes

31. Section 3 Meiosis
Chapter 8
Meiosis I
Meiosis I – original cell produces 2 new cells, each containing 1 chromosome from each homologous pair.
New cells contain half the number of chromosomes of original cell, however, each new cell contains two copies (as chromatids) because the original cell copied its DNA before meiosis I

32. Section 3 Meiosis
Chapter 8
Meiosis II
Meiosis II occurs in each cell formed during Meiosis I and is not preceded by the copying of DNA
Meiosis II includes prophase II, metaphase II, anaphase II, and telophase II
Four new haploid cells result

33. Section 3 Meiosis
Chapter 8
Meiosis II
Prophase II – spindle fibers form and begin to move chromosomes toward middle of the dividing cell
Metaphase II – chromosomes move to middle of the dividing cell, -each chromatid faces opposite of the dividing cell

34. Chapter 8 Meiosis II Anaphase II
Section 3 Meiosis
Chapter 8
Meiosis II
Anaphase II
– chromatids separate and move toward opposite poles of the cell
Telophase II
-nuclear membrane forms around the chromosomes in each of the four new cells
Cytokinesis II
four new haploid cells
Each of the new cells contain half of the original cell’s number of chromosomes

35. Section 3 Meiosis
Chapter 8
Stages of Meiosis

36. 1n 1n Chapter 8 Development of Gametes aka Sex Cells
Section 3 Meiosis
Chapter 8
Development of Gametes aka Sex Cells
Spermatogenesis is the process by which sperm cells are produced.
Oogenesis is the process that produces mature egg cells. 1n 1n

37. Meiosis in Male and Female Animals
Section 3 Meiosis
Chapter 8
Meiosis in Male and Female Animals 2n 1n

38. Chapter 8 Sexual Reproduction
Section 3 Meiosis
Meiosis Video
Chapter 8
Sexual Reproduction
Sexual reproduction is the formation of offspring through meiosis and the union of a sperm and an egg.
Offspring produced by sexual reproduction are genetically different from their parents.