Ges 103 Lec 9 + 10

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Mitosis

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is cell division that produces identical cells for growth and repair.

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Before cell division the DNA in the original cell is?

Back 2

doubled

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Chromosomes

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made of DNA and proteins, these are visible structures

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Centromere

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Waht attatches two identical pieces of DNA

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Sister Chromatid

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Two pieces of identical DNA joined with a centromere

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Pinch

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When Sister Chromatids spread apart in a cell so that it can pinch itself into two cells.

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Mitotic Spindle

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Network of protein fibers that forms and stretches across the cell. The mitotic spindle is what pulls the chromosomes to either end.

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Somatic Cells

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Body Cells. They all have equal numbers of chromosomes. Humans have 46.

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Pairs

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Chromosomes come in pairs, one from each parent.

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Chromosome Number (n)

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Diploid = 2n = Body Cells (2 sets)
Haploid = n = Sperm or Egg Cells (1 Set)

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1. Interphase

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90% of Existence. Prepares for Cell Division. DNA is copied, but can not be seen, because it has a nuclear envelope around it.

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2. Prophase

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Nuclear Envelope drops off, chromosomes become visible. Mitotic Spindle Forms.

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3. Metaphase

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Sister chromatids are pulled to the "equator" of the cell, where they are lined up in a single row.

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4. Anaphase

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Sister Chromatids seperate and are pulled to opposite poles. Now each chromatid is independant.

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5. Telophase

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Begins when chromatids arrive at poles. Nuclear envelope forms again around each set of chromosomes.

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6. Cytokinesis (animal)

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contractile microfilaments pull the plasma membrane inward and pinches the cell in two.

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6. Cytokinesis (plant)

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Plant cells cannot be pinched because they have a cell wall. They form a cell plate with cellulose and separate the cells that way.

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Apoptosis

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Cells that are destined to die. i.e. Skin in-between fingers and toes.

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Gamete Shuffle

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Meiosis shuffles the alleles during gamete formation (GAMETES = eggs or sperm), and
fertilization produces offspring with unique combinations of alleles.

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Variation

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By shuffling chromosomes alone, humans can have 8 million different gametes, so two humans can have 64 trillion genetically different kids

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Meiosis vs Mitosis

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Meiosis has two series of divisions, Meiosis 1 and 2

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Meiosis 1

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During meiosis 1, the sister chromatids do not line up across the equator in a single row. Instead, they line up 2 deep, and the sister chromatids are in tact when they are pulled toward the poles.

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Meiosis 2

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During meiosis 2, The sister chromatids line up again in metaphase. This time, they split before they seperate. The cytoplasm then divides again, resulting in 4 haploid cells.

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Zygote

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Fertilized egg. When this is created through fertilization, the diploid number of chromosomes is restored.