1. The
Cell Cycle

3. The Cell Cycle
The cell cycle is the repeated pattern of GROWTH and DIVISION that occurs in eukaryotic cells.
There are three parts of the cell cycle:
1. INTERPHASE – cell growth & copying DNA
2. MITOSIS – division of the nucleus
3. CYTOKINESIS – division of the cytoplasm
Cells spend about the majority of their time in INTERPHASE

5. Interphase Interphase is divided into 3 phases:
G1 (Gap 1): the cell GROWS and makes PROTEINS
S (Synthesis): the chromosomes REPLICATE (x2);
form identical sister chromatids held together by a centromere
G2 (Gap 2): the cell continues to grow, produce proteins for cell division and PREPARES for cell division

6. Interphase

7. CHROMATIN vs. CHROMOSOME
During interphase, the cell’s genetic material is visible as a stringy material called CHROMATIN
During PROPHASE, the chromatin condenses and supercoils into CHROMOSOMES
A chromosome consists of two identical SISTER CHROMATIDS held together by a CENTROMERE.

8. Sister
chromatid
centromere
chromosome
DNA
double helix

10. Mitosis
Mitosis begins with one cell, and produces two identical “DAUGHTER CELLS” that have the SAME DNA as the parent cell
For example, a normal human skin cell has _____ chromosomes.
If the skin cell undergoes mitosis, the result will be TWO new skin cells, each with _____ chromosomes. 46 46

11. Mitosis
4 strands (2 sister chromatids) break apart so each new cell has one double stranded chromosome.
Mitosis follows interphase and is divided into 4 phases

12. Mitosis Mitosis consists of four phases: (PMAT) Prophase Metaphase
Anaphase
Telophase

13. Mitosis

14. Prophase The CHROMATIN CONDENSES into visible chromosomes
The nuclear envelope DISAPPEARS
The CENTRIOLES SEPARATE and move to opposite ends of the cell
SPINDLE FIBERS FORM and spread out across the center of the cell

15. PROPHASE

16. Metaphase Chromosomes LINE UP ACROSS THE MIDDLE of the cell
Spindle fibers connect the CENTROMERE of each chromosome to the POLES
(Shortest phase of mitosis)

17. metaPHASE

18. Anaphase Centromeres that join the sister chromatids split
The CHROMATIDS SEPARATE
Separated chromatids move to OPPOSITE ENDS of the cell

19. anaPHASE

20. Telophase The CHROMOSOMES UNCOIL and become chromatin once again
The Nuclear Envelope REFORMS around the chromatin at each end of the cell
Spindle fibers DISSOLVE
CYTOKINESIS begins

21. teloPHASE

22. Cytokinesis Cytokinesis is the DIVISON OF THE CYTOPLASM IN PLANTS
IN ANIMALS
a CLEAVAGE FURROW forms and the cell membrane “pinches” inward between the two nuclei
IN PLANTS
The cell cannot “pinch” inward because of the cell wall, so a CELL PLATE forms between the two nuclei

23. Cytokinesis in animal cells

24. Cytokinesis in plant cells
Cell plate