1. October 25, 2011
Mitosis!

2. Brainteaser
You enter a dark room. You have only one match. There is an oil lamp, a furnace, and a stove in the room. Which would you light first?

3. Lets’ Review
In DNA replication, what protein unwinds or cuts apart the hydrogen bonds holding the nitrogenous bases together?
Replication is thought to be ____-________
What are the four nucleotide bases?
What are the complementary bases?

4. Cell Growth and Reproduction
Mitosis

5. Mitosis produces identical offspring (2N---2N)

6. Cell Growth and Reproduction
So how does cell division take place?
Scientists recognized that just before cell division, short stringy structures appeared in nucleus
These structures are called chromosomes in form of chromatin

7. Cell Growth and Reproduction
Before cell division, chromosome is in
spaghetti-like CHROMATIN state
As cell division begins, chromosomes take
on a new tightly packed shape
Genes are found on chromosomes
DNA makes up Genes
DNA is made up of base pairs.
A - T
G - C

10. Cell Growth and Reproduction
INTERPHASE:
DNA has replicated, but has not formed the condensed structure of chromosome. They remain as loosely coiled chromatin.
The nuclear membrane is still intact to protect the DNA molecules from undergoing mutation.

11. Cell Growth and Reproduction
MITOSIS:
As cell gets to the maximum size, it begins to undergo MITOSIS (cell division)
FOUR PHASES:
Prophase
Metaphase
Anaphase
Telophase

12. Cell Growth and Reproduction
PROPHASE – 1st Stage of Mitosis
Long stringy chromatin coils up into visible chromosomes
Spindle fibers
Disappearing nuclear envelope
Doubled Chromosome

13. Cell Growth and Reproduction
PROPHASE – 1st stage of Mitosis
Towards end of Prophase, nucleus begins to disappear as nuclear envelope and nucleolus disintegrate.
The nuclear membrane and nucleolus are no longer visible.
Centrioles begin to migrate to opposite ends of cells

14. Cell Growth and Reproduction
PROPHASE: Let’s break it down
Chromosomes coil up
Sister Chromatids form
Nucleolus and Nuclear Envelope disintegrates
Centrioles migrate to opposite ends
Spindles form between Centrioles

15. Cell Growth and Reproduction
2nd Phase of Mitosis: METAPHASE
The spindle fibers attach themselves to the centromeres of the chromosomes
The chromosomes align at the equator or middle plate.

16. Cell Growth and Reproduction
2nd Phase of Mitosis: METAPHASE
One sister chromatid’s spindle fiber extends to one pole while other spindle fiber extends to opposite pole.

17. Cell Growth and Reproduction
2nd Phase of Mitosis: METAPHASE
What is the importance?
This arrangement of the chromatids ensures that each new cell receives identical and complete set of chromosomes (DNA)

18. Cell Growth and Reproduction
3rd Phase of Mitosis: ANAPHASE
Beginning of sister chromatid separation
Centromeres split
Chromosomes separate from each other
spindle fibers shorten and pull apart chromatids to opposite poles

19. Cell Growth and Reproduction
4th Phase of Mitosis: TELOPHASE
Begins once chromatids reach opposite poles
Chromosomes begin to unwind and return to chromatin
Spindle fibers breaks down

20. Cell Growth and Reproduction
4th Phase of Mitosis: TELOPHASE
Nucleolus and nuclear envelope reappears around new set of chromosomes
Double membrane forms between two new nuclei
Two daughter cells formed

22. Cell Growth and Reproduction
Cytokinesis:
After Telophase, cell’s cytoplasm divides
Animal Cells: At end of Telophase, plasma membrane pinches off forming two separate cells.
Plant Cells: Cell plate laid across cell’s equator—there is no pinching off. Cell membrane forms around each cell and new cell walls form on each side of cell plate

23. plant
cytokinesis

24. Cell Growth and Reproduction
Cytokinesis:

27. Cell Growth and Reproduction
What are the results of Mitosis?
Single Cell organism remains a single cell but has replicated itself
Multicellular organisms have grown or created another cell that will work together as tissue to perform a certain function

28. Cell Growth and Reproduction
Recall BIOLOGICAL ORGANIZATION:
Cells
Tissues
Organs
Organ System
Organisms

29. Cell Growth and Reproduction
Section Quiz:
The stringy structures in the cell nucleus that contain DNA are __________.
Centromeres
Chromatin
Genes
Chlorophylls