Chap. 8: Chromosomes, Mitosis, and Meiosis

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Chap. 8 Chromosomes, Mitosis, and Meiosis

• Chromosomes

Centromere- attaches chromatids
chromatid
Every species has specific of chromosomes. Ex.
Chimps- 48, Protozoa- 300, Humans 46. Number
does not indicate complexity.
chromosome
2
-- sexually reproducing organisms have
chromosomes in pairs called homologous
chromosomes.

• Diploid (2N)
• Contains 2 of each chromosome. One from mom, one
  from dad
• Called body cells or somatic cells
• Most cells in body

• Haploid(1N)
• Contains one of each chromosome
• Called sex cells (sperm and egg) or germ cells.

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II. Cell Cycle the complete cycle of a cell
replicating.
anaphase
telophase
mitosis
cytokinesis
metaphase
G1 - growth
prophase
G2 growth preparation of cell division
S growth duplication of DNA
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G1 phase cell is increasing in volume. If ratio
of volume to surface area reaches a certain point
then cell passes into S phase. not all cells
divide nerve cells (brain and spinal cord)
just get bigger or longer.Stay in G1 phase .
Cant replace if damaged.
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A. Steps of Cell Cycle

• 1. Interphase longest, cell getting bigger. DNA
  intertwined. Includes G1, S, and G2 phases.
• 2. Prophase nucleus disappears and chromosomes
  form. Spindle fibers appear (made from
  centrioles).

Spindle fiber
X x x x x x X x x x
Centriole
chromosomes
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3. Metaphase (middle) chromosomes line up at
the center or equator.
X X X X X X X X X X
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4. Anaphase chromosomes separate and move to
poles or ends.
X X X X X X X
X X X X X
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5. Telophase final phase of mitosis- centrioles
spindle fibers disappear and cell begins to
divide.
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6. Cytokinesis

• the complete splitting of the cell, including
  dividing up all organelles within the cytoplasm.
• --- end of cell cycle 2 cells exactly alike.
• --- steps 2,3,4,and 5 makeup mitosis

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Mitosis Pics