1. Mitosis
H Biology
Lane Tech

2. What is the structure of a chromosome?
Where in a cell is the genetic material/chromosomes located?
Nucleus
Chromatin is an uncoiled mass of DNA and histone proteins
Exists in this form the majority of the time!
As a cell prepares to divide it coils
up & condenses:
We call these CHROMOSOMES (condensed
DNA)
Histones are proteins that help DNA condense

3. Genes Segments of DNA (that make up the chromosome) are called genes
A gene is a piece/segment of DNA that stores genetic information

4. What happens to chromosomes during cell division?
What needs to be done to a chromosome before it can divide?
It must DUPLICATE! (DNA Replication)
After duplication each chromosome consists of 2 identically joined copies  Sister Chromatids
Sister Chromatids are held together by centromeres
Chromatin
Chromatid
Sister
Chromatids (condensed, duplicated chromosome)
Recall that each chromosome has already been copied (s phase). Thus, the chromosomes look similar to an “X” in which the L and R chromatids are idential DNA double helixes…we call them SISTER CHROMATIDS to illustrate that they have already been REPLICATED

5. What is Mitosis!?
Mitosis is the process where cells divide to produce new cells
- Occurs in healing, growth, day-to-day life
ALL eukaryotic organisms produce new cells through mitosis

6. Cell Cycle Consists of 2 broad stages
1. Growing Stage called Interphase
2. Cell Division called Mitotic Phase (M Phase)
The majority of the cell cycle (90%) is spent in Interphase

7. Interphase Occurs before mitosis begins
Interphase is divided into 3 sub sub-phases:
G1 Phase
S Phase
G2 Phase

8. G1 Phase
G1 – Cell begins to grow because it needs to increase its surface area before dividing
Growth continues through S Phase
Organelles increase in number and size
Chromosomes appear as threadlike coils
Made of Chromatin, a combination of DNA and protein molecules

9. S Phase (Synthesis) S Phase – DNA replication occurs
Chromosomes are copied (# doubles)
The region where the two chromatids are joined tightly together is called the centromere.
Each chromosome is single  replication occurs and then the chromosomes are doubled each consisting of two sister chromatids

10. G2 Phase G2 – Continues growing & prepares for cell division
As the cell prepares to divide, its chromatin fibers condense, becoming the compact structure we call a chromosome.

11. After Mitosis, cells RE-ENTER G1… process starts again
Recap…
THEN mitosis truly begins…
G1 – growth
S phase – doubling DNA
G2 – growth again…

12. Refresher……. The Cell Cycle: G1 phase: Growth S phase: DNA replication
G2 phase: Preparation for cell division
M phase: Mitosis and Cytokinesis

13. Mitotic Phase After Interphase, Mitotic Phase begins:
Two parts of M Phase:
Mitosis
the nucleus and doubled chromosomes divide  create two identical daughter cells
Cytokinesis
- the process where the cytoplasm is divided in two
Cytokinesis usually begins before Mitosis is completed.

14. IPMATC Interphase Prophase Metaphase Anaphase Telophase Cytokinesis
I Play Monopoly At Camp

15. Prophase: First phase of Mitosis: Nuclear envelope breaks down
Chromatin becomes tightly coiled = chromosomes
Spindles (made by the
centrioles) begins to
form in the cytoplasm
Centrioles
Spindles
92 chromosomes of DNA at this point

16. Prophase:
2. Centrioles move
DNA supercoils into chromosomes

17. Metaphase Second phase of Mitosis: Nuclear membrane disappears
Chromosomes attach to the spindle at the centromeres
Chromosomes line up in the middle of the cell forming an equator
92 chromosomes at this point

18. Metaphase:

19. Anaphase Third phase of Mitosis: Spindle pulls apart chromosomes
Chromatids separate at the centromere and move towards each end
Each chromatid is now considered its own chromosome
Still 92 chromosomes….

20. ***Remember that each chromatid has the same DNA so each is now its own chromosome***
Anaphase:

21. Telophase Fourth phase of Mitosis: Chromosomes reach end of spindle
Spindle breaks down
Cleavage furrow begins to form
Nuclear membrane begins to reform
NOW each cell has 46 chromosomes (23 pairs)

22. Telophase:
Spindle fall apart
Cleavage furrow

23. Cytokinesis Final Phase of Cell Division/M Phase
Cleavage furrow pinches all the way through
Result is two new cells
2 NEW cells then enter the cycle and Mitosis begins again! YAY!
G1, S, G2 (Interphase)
PMAT & Cytokinesis
Each new cell at the end of mitosis is DIPLOID
has a full set of chromosomes (46)
Officially 2 new cells with 46 chromosomes EACH

24. Early Prophase Late Prophase Metaphase Anaphase Telophase
Nuclear Envelope Breaks Down
Centrosomes continue to separate
Chromosomes attach to MTs
Nuclear Envelope Intact
Centrosomes starting to separate
Sister Chromatids Separate
Centrosomes often separate further
Nuclear Envelope Reforms
Cell Membrane divides cell in two
Chromosomes become centered in middle of spindle

25. What is Apoptosis?
Apoptosis is also called Programmed Cell Death

26. What are Tumors? Tumors: A mass of cells Caused by out-of-control cell
division
2 types:
Benign
Mass of normal cells
Remain at original site
Malignant
Mass of cells from reproduction of cancer cells

27. What is Cancer?
Disease caused by disruption of the control of cell division
Uncontrollable cell division
Can spread cancer cells throughout the body
METASTASIS
Cancer “masses” displaces normal tissue

29. What are the treatments for cancer?
Surgery
Radiation Therapy
High energy radiation disrupts cell division
Chemotherapy
Drugs disrupt cell division
Anti-mitotic drug freezes spindle fibers