BIOLOGY Cell Growth and Reproduction

If a cell is too big, then nutrients cannot get to all of its organelles quickly enough, and if wastes can't move out of the cell because it is too large, then the cell will die.

Cell reproduction is needed to allow for the cell to have many generations, and to mutate and have changes in genes.

• 1. Interphase (90%)
• 2. Mitosis
• 3. Cytokinesis
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• 1. Gap 0 (G0) When a cell leaves the cycle and stops dividing
• 2. Gap 1 (G1) Cells increase in size and organelles are doubled. (A checkpoint occurs at the end of G1)
• 3. S Phase DNA replication occurs
• 4. Gap 2 (G2) Cell continues to grow and make new proteins (A checkpoint occurs at the end of G2)
• 

• 1. Prophase I - Homologous chromosomes pair up and form tetrad, crossing-over occurs
• 2. Metaphase I - Homologs line up along equator
• 3. Anaphase I - Spindle fibers move homologous chromosomes to opposite ends
• 4. Telophase I - Cytoplasm divides, two daughter cells are formed
• 5. Prophase II - Chromosomes are in nucleus
• 6. Metaphase II - Chromosomes line up along equator, not in homologous pairs
• 7. Anaphase II - Chromatids separate
• 8. Telophase II - Nuclear membrane reforms, cytoplasm divides, four daughter cells formed
• 

• 1. Prophase - Chromosomes appear, centrioles separate and take opposite sides, chromosomes attach to spindles, nucleolus disappears, nuclear membrane breaks down
• 2. Metaphase - Shortest phase, chromosomes line up across the center of cell
• 3. Anaphase - Centromeres split, spindles grow, chromosomes separate into two groups near poles
• 4. Telophase - Chromosomes uncoil into chromatin, nuclear membrane reforms, spindles break apart, nucleolus reappears
• 

• 1. Meiosis creates four cells, mitosis creates two
• 2. Meiosis only occurs in reproductive cells, mitosis occurs in all other cells
• 3. Meiosis has 8 stages, mitosis has 4