Mitosis+Assignment


 * Work in teams of 2 or 3 to a laptop.**


 * Part I.** **Meiosis Introduction**
 * 1) Obtain a "Meiosis - Reduction Division" packet. [[file:Biology II- Meiosis Worksheet.doc]]
 * 2) Open the "Campbell Animations" link from my collect folder, click "launch" choose Select "Chapter 13" and "Activities" and "13B Meiosis Animation" Go through the Animation and fill in the packet. (Can only access from within ISB) From home: try this [|Meiosis Turotial]
 * 3) Whatever you don't finish is homework.

Go [|here] to see a comparison of meiosis and mitosis side by side, VERY USEFUL! Try your luck at moving the chromosomes to the appropriate places [|here].
 * Part II. Review and Comparison.** (at home)

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 * Extension Questions:**

1) What makes chromosomes actually move? In cell division, the spindle fibers break apart and moves the chromosomes along to the each poles.1205596490

Spindle fibers rip apart the chromosomes and move them to the poles. 1205761821

2) How does animal and plant cell mitosis differ? Cytokinesis: In animal cells, cell membrane pinches into the center of the cell, creating a cleavage furrow. In plant cells, vesicles fuse at the midline of the cell, constructing a membrance-bound cell wall called the cell plate. 1205651670

Animal cells: - cytonkinesis is performed using a contractile ring (consists of proteins wrapped around the divinding cell) - as the proteins contract, they pinch the cell in two parts at the equator of the cell - creates a deep groove known as the cleavage furrow - cleavage furrow enlarges until two new cells are formed 1205761821

Plant cells: - presence of cell wall prevents pinching action - cytokinesis in plant cells requires the construction of a new cell between the two daughter cells - begins as a flattened disk known as the cell plate - eventually becomes an actual cell well that separates daughter cells from each other 1205761821

3) How is cell division controlled? What happens of the cell cycle is not regulated? - telomeres (specialized chromosome tips) signal when cell division should stop (some exceptions) - they are composed of six repeated six base sequence that are lost during cell division. They shorten and at a certain point the signal is created. The following signal that it is time for the cell to divide: - contact inhibition and hormonal control - cyclin and kinase control - control at the tissue level - stem cells and cell populations 1205761821

When it is not regulated (cancer cells as an example): - cancer cells lack contact inhibition - a cancer cell lacks a mitotic "brake" - cancer cells repeatedly go through the cell cycle and, essentially, never die. They grow uncontrollably. - they have abnormal nuclei with mutated chromosomes - cancer cells form tumors. Since they grow uncontrollably, they continue to divide forming large amounts of cells. 1205761821