1. The Cell Cycle!

2. Objectives
• The reproduction of cells and organisms accounts for the continuity of life.
• The work of a cell is carried out by many structures made up of a variety of molecules.
• Understanding the processes and functions of related structures found in unicellular and multicellular organisms.
• Illustration and explanation of how traits are passed from parent to offspring.

3. The Cell Cycle
Cell cycle: the regular sequence of growth and division that cells undergo
What happens during the cell cycle?
a cell grows, prepares for division, and divides into two new cells called “daughter cells”

4. Three stages of the cell cycle:
1.Interphase
2. Mitosis
3. Cytokinesis

5. Stage One: Interphase the first stage of the cell cycle
the period before cell division
While in interphase, the cell grows, makes a copy of its DNA, and prepares for division into two new cells

6. Interphase cont.. Cell Growth
first part of interphase where the cell grows to its maximum size
it then produces structures it need for division
new ribosomes are made
new enzymes are produced
copies are made of the mitochondria and chloroplasts

7. Interphase cont.. Copying the DNA
Replication: when the cell makes an exact copy of the DNA in its nucleus
After copying the DNA, the parent cell will have 2 identical sets of DNA.
This is important because each daughter cell must have a complete set of DNA.
If the DNA replication goes wrong, the daughter cells would not survive.

8. Stage Two: Mitosis What happens during mitosis?
the cell’s nucleus divides into two nuclei
one copy of the DNA is distributed into each of the two daughter cells
There are 4 phases of mitosis:
Prophase
Metaphase
Anaphase
Telophase

9. Phase 1: Prophase Chromatin in the nucleus condenses into chromosomes
Chromatin is threadlike and condenses into double-rod shaped chromosomes
Each chromosome has two rods. Each rod has an exact copy of DNA as the other.
Individual rods of the chromosomes are called chromatids.
The two chromatids are held together by a centromere to make the chromosome.

11. Two pairs of centrioles move to opposite side of the nucleus.
Spindle fibers form a bridge between the pairs of centrioles.
During prophase, the nuclear envelope breaks down.

12. PROPHASE

13. Phase 2: Metaphase
chromosomes attach to a spindle fiber (microtubule) at the centromere
attached chromosomes line up across the center of the cell

14. Phase 3: Anaphase Centromeres split
The two sister chromatids separate.
Once separated, the chromatids move to opposite ends of the cell.
The cell stretches outward as the ends are pushed out.

16. Phase 4: Telophase
Chromosomes start to stretch and look more like chromatin again.
A new nuclear envelope forms around each set of chromosomes

18. Stage 3: Cytokinesis Final stage of the cell cycle
What happens during cytokinesis?
the cytoplasm divides
organelles are distributed into each new cell
At the end of cytokinesis, two daughter cells have been made and each contain the same number of chromosomes as the parent cell.
Each cell then enters interphase and the cycle starts over.

20. Cell Division Gone Wrong
What happens when cell division goes wrong?
apoptosis (cell suicide)
cancer (uncontrolled cell growth)