Cellular Division

Dani Sustek

A Video of Cell Cycle, Mitosis, and Meiosis.

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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)

1. Prophase- Homologous chromosomes pair up and form tetras.

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