1. Mitosis & Cell Division
8th Grade
Unit 2
ChL4, Section 1

2. Growth of living things depends on cell division and the process of mitosis.

3. The Cell Cycle
The cell cycle is a series of events that takes place from one cell division to the next
Length of time to complete the cycle is different for different types of cells
Bean plants is 19 hours, animal embryos are less than 20 minutes
Occurs in 3 major stages
Interphase, mitosis, cytokinesis

5. Interphase is the longest part of the cell cycle
A period of growth and development
Inactive cells (nerves and some muscles) are always in interphase
Actively dividing cells will copy their DNA/chromsomes and prepare for division during interphase
Before a cell divides, a complete copy of all of its hereditary material must be made so each new cell has a complete copy

6. Mitosis & Cell Division
After DNA is copied during interphase, the cell must divide (enters mitosis stage)
Mitosis has 4 phases
Prophase, metaphase, anaphase, telophase
PMAT
Copied chromosome has 2 identical strands called chromatids
Held together at the centromere
Resembles the letter X
Happens during interphase of cell cycle

8. Prophase
During prophase (1st), the chromatids are visible and spindles begin forming
The nuclear membrane and nucleolus disintegrate

9. Metaphase
In metaphase (2nd), pairs of chromatids line up at the center of the cell
Spindle fibers attach to the centromere from each side of the cell

10. Anaphase
During anaphase (3rd), the centromere divides the chromatids, and spindle fibers begin shortening
Chromatids separate and begin moving to opposite sides of the cell
Now called a chromosome (a single copy of DNA)

11. Telophase
In the final phase of mitosis, telophase (4th), cytoplasm begins to divide
Nuclear membrane forms around each set of chromosomes
Spindle fibers disappear
Cell membrane begins pinching inward between the 2 new nuclei

12. The final stage of the cell cycle is cell division, also called cytokinesis
Cytoplasm separation and cell membrane completely pinches in to create 2 new cells (only in animal cells)
A cell plate must form between the 2 new nuclei of plant cells, which will become the cell wall of the new cells
Once the new cells have separated they enter back into interphase
Undergo growth and development

13. Asexual Reproduction
Plants may reproduce asexually by repeating the cell cycle multiple times
One plant grows from each new sprout
Known as budding and regeneration
Bacteria are prokaryotic and don’t have a nucleus
Reproduce by a simple process known as binary fission
Genetic material is copied and cytoplasm divides, membrane pinches inward to form 2 new cells