1. Cell Division
Part One: Mitosis

2. In this lesson…
Explain the difference between double and single stranded chromosome, chromatin and chromatid
List the steps of mitosis and describe what happens in each
Identify what stage of mitosis a cell is in by looking at the chromosomes
List three reasons cells divide by mitosis
Describe cytokinesis

3. In the nucleus
In non-dividing cells, the genetic material is stored as thin DNA super coils called CHROMATIN
When a cell divides, the chromatin will shorten and thicken into CHROMOSOMES
One strand of a double stranded chromosome is called a CHROMATID

4. Mitosis
MITOSIS: a process by which the nucleus of a cell divides while maintaining the chromosome number
One cell  two cells
New cells have identical genetic material (DNA) of the parent cell
Four stages of division (Prophase, Metaphase, Anaphase and Telophase - PMAT) plus a period of growth and metabolism called Interphase

5. The Cell Cycle

6. Interphase Period between divisions Longest part of the cell cycle
Cell is growing and metabolizing
Nuclear membrane present
Genetic information in the form of chromatin and cannot be seen with a microscope
Before division each strand of DNA will replicate (copy) itself to become double stranded
Near the end of interphase the DNA begins to condense (shorten)

7. Interphase

8. Draw a double stranded chromosome
Draw a double stranded chromosome. Label chromosome, chromatid and centromere
Chromatid
Chromosome
Chromatid
Centromere

9. Phase One: Prophase
Chromatin contracts and becomes visible (spaghetti). It is now called CHROMOSOMES
Each is a double chromosome with a pair of SISTER chromatids which are joined to each other by a centromere
Chromosomes begin to move towards the equator (center) of the cell
Nuclear membrane disintegrates (breaks down)
CENTRIOLES will form SPINDLE FIBERS that will attach to each centromere and move around the chromosomes

10. Prophase

11. Phase Two: Metaphase
The centromeres of each chromosome line up along equator ( looks like praying hands)
Centromeres divide so the doubled chromosomes become two identical single stranded sister chromatids
Centrioles are now at the poles of the cell and are attached to each centromere by spindle fibers

12. Metaphase

13. Phase Three: Anaphase
The spindle fibers begin to shorten and the chromosomes begin moving to opposite ends or poles of the cell (fingers)
Each side gets one chromatid from each double stranded chromosome

14. Anaphase
chromosomes

15. Phase Four: Telophase
Begins when single stranded chromosomes reach the poles
Chromosomes uncoil and turn into chromatin
Nuclear membrane reappears
Reverse of prophase
Division of the cytoplasm or CYTOKINESIS is completed by pinching off in animals or by building a cell wall in plants

16. Telophase

17. What’s the point of Mitosis?
Mitosis creates identical copies of cells for:
1. growth
2. Repair/regeneration of damaged tissue
3. Asexual reproduction (animals) or vegetative reproduction (plants)

18. Asexual Reproduction
Reproduction that involves only one parent; parent and offspring have identical genetics
No special reproductive cells or organs used to create offspring
Occurs through mitosis and cytokinesis
Both single and multi-celled organisms, plants and simple animals can reproduce asexually
In multi-cellular organisms, the offspring develop from undifferentiated, unspecialized cells from the parent
Usually a rapid form of reproduction

19. Binary Fission Simplest form of asexual reproduction
Parent divides into two approximately equal sized daughter cells
Bacteria: circular chromosome attaches to plasma membrane then replicates, cell wall separates each copy
Protozoa: eg. Amoeba become circular and use mitosis

20. Budding
New individuals develop from small outgrowths of the parent (buds)
May develop colonies (sponges) or break off to be individuals (hydra, yeast)
Some organisms can both bud and reproduce sexually

21. Spores
Specialized single cells that are released from the parent organism, germinate and grow by mitosis
New cells differentiate to form a new organism
Can reproduce quickly and in large quantities
Often have thick protective coats
Eg. Fungi, algae, protozoa

22. Regeneration The ability to regrow lost body parts
Some animals can regrow entire new organisms from parts
Ability to regenerate decreases as organisms increase complexity
Even simple organisms that can regenerate entire organisms generally prefer to utilize a different method to reproduce

23. Vegetative reproduction
MERISTEM: area on plant with unspecialized cells (cells that can become any kind of cell) that frequently divide using mitosis
Meristematic cells can be found in the vegetative structures of a plant (roots, stems, leaves)
Given proper treatment, meristem cells can reproduce mitoticlly then differentiate into new independent plants
Structures include bulbs, corms, tubers, runners, rhizomes
Can also be artificially propagated using cuttings, layerings or grafting

24. Bulb short underground stem with thickened storage leaves
small new bulbs sprout from the old ones
Eg. onions, tulips

25. Corm short underground stems with no fleshy leaves
Eg. gladiolas, crocuses

26. Tuber enlarged part of an underground stem that contains stored food
potatoes (eyes are tiny buds)

27. Runner AKA stolon is a stem that runs sideways and contains buds
Eg. strawberry

28. Rhizome
a stem that grows sideways under the ground
ferns, irises

29. Cutting
a stem, root or leaf cutting used to make a new plant

30. Layering part of a stem is bent and covered in soil
once it roots the original can be cut off
Eg. raspberries, roses

31. Grafting
stem or bud removed from one plant and permanently joined to another plant
Eg. grapes and many seedless fruits