1. Chapter 8: Cell Reproduction

2. Review Organelles Centrioles Mitotic Spindle fibers Nuclear envelope
Made of microtubules
Acts as anchors in cell division
Mitotic Spindle fibers
Two Main types
Kinetochore Fibers- Attach from centriole to centromere of chromosomes and assists in movement of chromosomes
Polar Fibers – Extend from pole to pole and keep the shape of the cell during cell division
Nuclear envelope
Double Phospholipid bilayer surrounding nucleus
Allows selective passage of RNA and other material
Nucleolus
Dense area where DNA is concentrated in the nucleus

3. Section 8.1 Chromosomes Chromosome Structure Chromatid Centromere
Rod-shaped and made of DNA and proteins called histones
Two full copies of DNA
Form it takes before cell division
Has two identical halves called chromatid
Chromatid
Half of the chromosome
One full copy of DNA
Attached in the center
Centromere
Center where chromatids are
held together
Chromatin
Less tightly coiled DNA-protein complex
Tin = thin *Think spaghetti
Form taken during transcription
Chromatid is

4. Section 8.1 Sex Chromosomes Autosomes Determine gender of the organism
May carry genes for other characteristics
Either X or Y
Female = XX Male = XY
One pair (or two chromosomes)
Autosomes
Remaining chromosomes
Contain genes for many traits
22 pairs (or 44 chromosomes)

5. Section 8.1 Homologous Chromosomes Karyotype
Two copies of each autosome
One copy from each parent
Same size and shape
Carry genes for the same trait
Karyotype
Photomicrograph of chromosomes
Notice there are 22 pairs of autosomes and 1 pair of sex chromosomes
What is the gender of this organism?

6. Section 8.1 Diploid Haploid
Cells that are diploid contain two autosomes from each homologous pair and two sex chromosomes
Abbreviated as 2n
Memory key * di = two
Occurs in all cells except sperm and egg cells
Haploid
Cells contain only one set of chromosomes
Therefore, half the number of chromosomes of a diploid cell
Abbreviated as 1n
Memory key * hap = half
Sperm cell (1n) and egg cell (1n) create a diploid cell (2n)

7. Section 8.1
Notice high number of chromosomes in fern compared to humans!

8. Section 8.1
Homework
Review questions on p. 153 #1-5

9. Section 8.1 Review Answers
Name the proteins that DNA wraps around to form a chromosome in eukaryotic cells.
Histones.
How do the structure and location of a prokaryotic chromosome differ from that of a eukaryotic chromosome?
A prokaryotic chromosome consists of a circular DNA molecule. Eukaryotic chromosomes are rod-shaped, associated with histone and nonhistone proteins, and found within the cell’s nucleus.
Does chromosome number indicate whether an organism is a plant or animal? Explain.
No. For example, chimpanzees have the same number of chromosomes as potatoes or plums.

10. Section 8.1 Review Answers
4. Contrast sex chromosomes with autosomes.
Sex chromosomes determine the gender of an organism. Autosomes are all of the other chromosomes in an organism.
5. Using Table 8-1, list the haploid and diploid number of chromosomes for each organism.

11. Section 8.1 Review Answers
Organism
Diploid # Chromosomes
Haploid # Chromosomes
Adder’s tongue fern
1262
631
Carrot 18 9
Cat 32 16
Chimpanzee 48 24
Dog 78 39
Earthworm 36
Fruit fly 8 4
Garden pea 20 10
Gorilla
Horse 64
Human 46 23
Lettuce
Orangutan
Sand dollar 52 26

12. Section 8.2 Cell Cycle Repeating set of events in the life of a cell
Interphase
Time between cell divisions
Three phases
G1 – Cell growth
S – DNA is copied
G2 – Growth and prep for cell division
Cell division
Two phases
Mitosis – Nucleus of the cell divides
Cytokinesis – Division of the cell’s cytoplasm

13. Section 8.2 Cell Division Prokaryotes
Remember: Has cell wall, no nuclei, no membrane-bound organelles
Binary fission
Division of prokaryotic cell into two offspring cells

14. Section 8.2 Cell Division (cont’d) Eukaryotes Mitosis Cytokinesis
Division of the nucleus
Four stages (Prophase, Metaphase, Anaphase, Telophase)
Cytokinesis
In animal cells, pinching of cell
membrane occurs
Cleavage furrow
In plants, cell plate formation

15. Section 8.2 Control of Cell Division Checkpoints = traffic signal
Three main checkpoints
G1 checkpoint
G2 checkpoint
Mitosis checkpoint

16. Section 8.2 (cont’d) Mitosis Prophase Metaphase = Middle
Tight coiling of DNA into chromosomes
Nucleolus and nuclear membrane break down
Centrosomes appear and move to opposite ends of the cell
Kinetochore fibers extend from kinetochore from each chromatid to centrosome
Metaphase = Middle
Kinetochore fibers move chromosomes to center of cell
All chromosomes line up in a single file line

17. Section 8.2 Anaphase Telophase Animation
Chromosomes separate at the centromere and chromatids move to opposite poles
Chromatids are now considered individual chromosomes
Telophase
Spindle fibers disassemble
Chromosomes return to less tightly coiled chromatin state
Nuclear envelope forms around each set of chromosomes
Nucleolus forms in each of the newly forming cells
Animation

18. Mitosis vs Meiosis Where do they occur? Why does it occur?
Mitosis – in the body cells (Somatic Cells)
Meiosis – in the germ cells (Sex Cells)
Why does it occur?
Mitosis
Asexual reproduction
Growth and development
To replace old cells
Meiosis
Formation of gametes (egg and sperm cells) that will be used in sexual reproduction

19. Mitosis vs Meiosis End result? MEIOSIS MITOSIS 46 46 23 23 46 46 23 23

20. Meiosis Also known as reduction division
Occurs in germ cells found in the ovaries and testes
Produces sex cells which are haploid
Occurs in two phases
Meiosis I
Reduces the number of chromosomes from diploid to haploid
Meiosis II
Produces four haploid daughter cells

21. Meiosis I

22. Meiosis II

23. Section 8.3
Results of mitosis vs. meiosis

24. Section 8.3 Development of Gametes Spermatogenesis Oogenesis
Polar bodies
Sexual reproduction

25. Why is meiosis important?
Increases genetic diversity in a population of species.
This helps to prevent organisms from mass extinction in the event of a plague or other disaster.
Allows animals to adapt to a changing environment (natural selection)