Cellular Division
Dani Sustek
A Video of Cell Cycle, Mitosis, and Meiosis.
Cell Cycle (Phases)
Part 1: Cell Division
A. M Phase- Division of the nucleus.
B. Cytokinesis- Division of the cytoplasm.
Part 2: Interphase
A. G1 phase- Offspring cells reach maturity.B. S phase- DNA and chromosomes are copied.
C. G2 phase- Cell waits to divide.
*RARE EXCEPTION*
- Cells can exit the cycle at G1 and enter G0 phase.
- No chromosomes copied; no cellular division.
- They die at maturity.
The Mitosis (Phases)
1. Prophase:
A. Chromosome pairs become shorter and thicker. (paired in "S" phase of Interphase)
B. Nuclear membrane begins to disappear.
C. 2 dark chromosomes appear next to the nucleus.
D. Spindle Fibers extend from the centrosomes as they move towards opposite sides of the cell, creating an early Mitotic Spindle.
2. Metaphase:
A. The Mitotic Spindle becomes easy to see.
B. Kinetochore Fibers move chromosomes towards the middle of the cell.
C. The nucleus disappears.
3. Anaphase:
A. The chromatids of each chromosome separate and move towards the centrosomes.
B. Each chromatid is considered one new chromosome.
4. Telophase:
A. Chromosomes reach opposite ends of the cell.
B. Spindle Fibers disappear.
C. Nuclei reforms around each set of chromosomes.
Meiosis (phases)
2. Anaphase- Spindle fibers move homologous chromosomes to opposite sides
3. Telophase-Nuclear membrane reforms, cytoplasm divides, 4 daughter cells formed
4. Metaphase 2- Chromosomes line up along equator, not in homologous pairs
5. Prophase 2- Chromosomes line up along equator, not in homologous pairs
6. Anaphase 2- Chromatin separate
7. Metaphase- Homologs line up alone equator
8. Telophase-Cytoplasm divides, 2 daughter cells are formed