1. Mitosis

2. Part 1: Chromosomes
Chromosome structure- DNA can exist in 2 different forms
A. Chromatin- DNA protein complex that is not coiled (thin)
B. Chromosome- rod-shaped; DNA is coiled tightly around proteins called histones. Formed before cell division. Each copy is called a chromatid.

3. FYI-The diagram will help you see the relationship in a cell.
1. Chromosomes are found in the nucleus 2. Chromosomes are made of DNA 3. Sections of chromosomes are called genes

4. Eukaryotic Chromosomes
All eukaryotic cells store genetic information in chromosomes
Most eukaryotes have between 10 and 50 chromosomes in their body cells
Human body cells have 46 chromosomes or 23 identical pairs

5. Eukaryotic Chromosomes
Each chromosome is composed of a single, tightly coiled DNA molecule
Chromosomes can’t be seen when cells aren’t dividing and are called chromatin

6. Compacting DNA into Chromosomes
DNA is tightly coiled around proteins called histones

7. Chromosomes in Dividing Cells
Duplicated chromosomes are called chromatids & are held together by the centromere
Called Sister Chromatids**

8. **Karyotype**
A picture of the chromosomes from a human cell arranged in pairs by size
First 22 pairs are called autosomes
Last pair are the sex chromosomes
XX female or XY male

9. The Y Chromosome Decides
Boy or Girl?
The Y Chromosome Decides
Y - Chromosome
X - Chromosome

10. II. Chromosome #’s-not related to complexity of species
Each organism has a distinct number of chromosomes, in humans, every cell contains 46 chromosomes. Other organisms have different numbers, for instance, a dog has 78 chromosomes per cell.
**There is no relationship between # of chromosomes and speed of mitosis. It all happens at the same rate.**

11. Chromosome #’s of various species
Organism
# of Chromosomes
Ant 2
Mosquito 6
Bearded Dragon 32
Cat 38
Pig
Axolotl 28
Dog 78
Hedgehog 90
Carp (highest animal)
104
Corn 20
Algae
148
Adder Fern (highest plant)
1260
Aulacantha (Protist)
1600

12. C. Sex Cells - also known as gametes
C. Sex Cells - also known as gametes. These cells contain half the number of chromosomes as body cells and are called HAPLOID. (for us = 23)
This is referred to as the N number.
So, our N number is 23.

13. If you have XX sex chromosomes - you are female.
If you have XY sex chromosomes - you are male.
During fertilization, sperm cells will either contain an X or a Y chromosome (in addition to 22 other chromosomes - total of 23). If a sperm containing an X chromosome fertilizes an egg, the offspring will be female. If a sperm cell containing a Y chromosome fertilizes an egg, the offspring will be male.

14. This is our Diploid number (2N).
D. Autosomes -all the other chromosomes; every cell of an organism has 2 copies of each autosome (2N). (N is 23, so 2N = 46)
This is our Diploid number (2N).
-We receive one copy from each parent, called homologous chromosomes- the same size and shape, and they carry genes for the same traits.
Homologous chromosomes, 2 pair

15. Cell Division- Prokaryotes
Cell Division in Prokaryotes.
1. Binary Fission- the division of a prokaryote into 2 identical cells.
2. Considered asexual (one parent)
Remember- prokaryotes are bacteria!

16. B. 3 General Stages
Chromosome makes a copy of itself, attached to the inside of the cell membrane.
Cell doubles in size
Cell wall forms between the 2 chromosomes and the cell divides, forming 2 equal cells.

17. Prokaryotes vs. Eukaryotes
Bacteria
All other organisms
Binary Fission
Mitosis
In all bacteria
All cells but sex cells
Have circular DNA
Have chromosomes
Replicates at 500 bp/min.
Replicates at 50 bp/min.
Produces identical organisms
Produces identical cells

18. What is Mitosis? The splitting or dividing of the nucleus
**Produces two genetically identical cells from one cell.
**Form of asexual reproduction, used for growth, repair, and reproduction.
Occurs only in certain types of cells (body cells except the sex cells), and in single-celled protists.

19. B. The Cell Cycle- Stages
                              
                              
                              
B. The Cell Cycle- Stages
(Use your WS for this part)
-not considered part of mitosis- is time between divisions.
1. Interphase (longest part of the cell cycle)
G1 (Growth 1)
S (Synthesis) - DNA copies
G2 (Growth 2) - cell prepares for division, organelles double

20. Interphase Cells spend most of its time in this phase
Cells are growing
DNA has to be replicated (all 2 meters of it)
Proteins are being produced
90% of all cells are in this phase
Three phases: G1, S, and G2

21. The Cell Cycle: G1 phase
Growth phase 1: proteins are made, cell grows to normal size.
If checkpoint here passed, cell will complete division
Some cells, like nerve cells, stay in this phase forever.

22. The Cell Cycle: S phase All nuclear DNA is replicated
Chromosome number doubles
Checkpoint: does cell have all its chromosomes doubled properly?

23. The Cell Cycle: G2 phase Cell volume increases
Centrioles with their microtubules form (centrosome)
Organelles double.
Checkpoint: is cell large enough to divide?

24. Photo of Interphase
                                             
Whitefish blastula cells

25. C. Mitosis Phases
This animation shows the process of mitosis.

26. 1. Prophase DNA shortens and coils into chromosomes;
nucleolus and nuclear
membrane break down and disappear;
centrioles appear and move towards opposite poles
Spindle fibers appear and attach to centromere.
Cells Alive Mitosis Animation (click here)

27. Early Prophase Photo
                                             

28. 2. Metaphase Chromosome pairs line up in the center by the centromere.
Move along spindle fibers.

29. Metaphase Photo
                                             

30. 3. Anaphase Chromosomes split at centromere.
Chromosomes move to opposite poles.

31. Anaphase Photo
                                             

32. 4. Telophase DNA lengthens and disappears.
nucleolus and nuclear membrane reappear.
centrioles and spindle fibers disappear.
Cell Splits (called cytokinesis), forming 2 equal cells.

33. Telophase Photo
                                             

34. Cytokinesis
The process by which the cytoplasm divides and one cell becomes two individual cells. The process is different in plants and animals:
Animal cells – cell membrane pinches in and separates the 2 cells = cleavage furrow
Plant cells- vesicles from the Golgi apparatus fuse at the midline forming a cell plate, which will become the cell wall.

35. Cleavage Furrow

36. Animation of cell plate forming

37. Now, name the phases as they occur in the animation.