1. 1.2 The Cell Cycle & Mitosis
“You Complete Me”
A process where one parent cell gives rise to two daughter cells- exact replicas of the original cell.

2. The Cell Cycle Importance of cell division: 1. Helps organisms grow.
2. Helps organisms repair.
3. Helps organisms reproduce. (simple organisms- reproduction)
(complex organisms- cell renewal)

3. Stages of Cell Cycle There are 3 stages to the cell cycle:
Interphase: growth and preparation
Mitosis: the process of duplicating the nucleus, (PMAT)
Cytokinesis:
division of cytoplasm and organelles

4. Stage 1: Interphase The longest of all 3 stages of the cell cycle
Onion root tip (on left side),
whitefish (on right side)
The longest of all 3 stages of the cell cycle
The cell grows and prepares to divide by duplicating its DNA and organelles so that it can be shared between the 2 new cells.
The DNA strands, chromosomes copy themselves, they are now identical strands of DNA
This now allows for the new cell to have the same genetic information as the parent cell.

5. Chromosomes duplicate Each strand is called a chromatid- duplication occurs during S of interphase when the DNA is in chromatin form and invisible under light microscope since it is too thin
centromere

6. Stage 2: Mitosis There are 4 main phases: Prophase, P Metaphase, M
Mitosis is the stage where the nucleus divides.
TWO copies of the DNA separate to opposite ends of the cell to make TWO new daughter cells.
There are 4 main phases:
Prophase, P
Metaphase, M
Anaphase, A
Telophase, T

7. Phase 1 of Mitosis: Prophase
Major processes during this phase:
Chromatin thicken and become more visible bodies- chromosomes, each pair is made up of identical strands tied together at centromere
Nucleolus disappears
Nuclear membrane around the nucleus begins to dissolve.
2 centrioles move to opposite ends of the cell
Mesh-like spindle fibres form between centioles
Chromosomes begin to attach to spindle fibres.

10. Phase 2 of Mitosis: Metaphase
Chromosomes (shaped like an X) attached to spindle fibers line up in the middle (the equator) of the cell
Single file created
Spindle fibers attach to the centromeres of the chromosomes.

11. Phase 3 of Mitosis: Anaphase
The sister chromatids separate and are pulled to opposite poles of the cell.
Look like a “C” or “V” because of the pull in the middle of the strand
Each separate chromatid is called a daughter chromosome.
One complete set of chromosomes moves to each end of the cell.

12. Phase 4 of Mitosis: Telophase
Spindle fibres begin to disappear
Daughter chromosomes stretch out, and become thin and invisible again. (changing into chromatin)
A new nuclear membrane begins to form around the nucleus at each end of the cell.
There are now 2 separate nuclei and the cell is ready to split into 2

13. Stage 3 of Cell Cycle: Cytokinesis
In this last stage of the cell cycle, the cytoplasm and other organelles are distributed to the two ends of the cell.
In an animal cell the cell membrane pinches in called the cleavage furrow.
In an plant cell, a cell plate forms instead
This separates the dividing cell into 2 new daughter cells.
Each daughter cell has a nucleus with a complete copy of the parents cell’s DNA and its own organelles.

14. cleavage furrow

15. This cycle this repeats
itself again!

16. Body Cell Chromosome Numbers During Mitosis
Parent Cell
2 Identical Daughter Cells

17. Can you identify these stages?B D C
A. Telophase B. Prophase C. Cytokinesis D. Metaphase
Answers:

18. Mitosis - Video

19. Homework
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2. Complete: Pg