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• *don’t need bellringer sheet* Take 5 minutes to study/quiz each other on cells (quiz today!)

Bellringer 10/23

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Bellringer 10/26• Write a

synonym for each of the following terms:–Within–Substance–Function 3

● When a living thing grows, what happens to its cells?

● The cells do NOT get bigger. Instead, the organism grows MORE CELLS

Cell Division

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UNIT 2 PART 2: CELL DIVISION

• All cells come from other cells.

• Each round of cell growth and division is called the cell cycle.

• For unicellular organisms, this is reproduction because it results in a new individual.

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In a cell with a nucleus two processes take place:

• Mitosis – The division of the nucleus– It has four stages

• Prophase• Metaphase• Anaphase• Telophase

• Cytokinesis– The division of the

cytoplasm– Forms two separate cells– These cells are genetically

identical

Before mitosis the cell must grow and prepare. This happens during Interphase, where the cell spends most of its time.

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Interphase

• From the end of one division to the beginning of the next: G1, S, and G2.

• This is when the cell grows, makes more organelles and proteins, and replicates the chromosomes so they become doubled.

• Centrioles in animal cells also replicate.

• During Interphase, the chromosomes are uncoiled, not visible, and called chromatin.

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Prophase• Doubled chromosomes become visible.– Each strand is called a

chromatid.– The chromatids are connected

by a centromere.

• Centrioles move to the poles.

• Microtubules form asters and the spindle apparatus that stretches from pole to pole.

• Nuclear membrane and nucleolus disappear.

chromatids

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Metaphase• Centromeres, which

are connected to spindle fibers, line up in the middle of the cell on the metaphase, or equatorial, plane.

• By the end of metaphase the centromeres divide and the chromatids become separate chromosomes.

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Bellringer 10/27

• What happens in interphase?

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Anaphase

• The chromosomes are pulled to opposite poles by the spindle fibers so that there is one complete set at each end of the cell.

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Telophase• The chromosomes

reach the poles and will uncoil again into chromatin.

• The spindles and asters disappear.

• A nuclear membrane forms around each set of chromosomes forming two daughter nuclei.

• Nucleoli reappear.

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Cytokinesis: The formation of two separate identical cells

• In animal cells the cell membrane pinches in until opposite sides touch and two new cells are formed.

• In plant cells a cell plate forms between the two daughter nuclei and forms a new cell wall.

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Bellringer 10/28

All your skin cells have 46 chromosomes. When a skin cell divides through mitosis, how many chromosomes does each daughter cell get?

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MITOSIS REVIEW - IPMAT

• Interphase – chromatin and replication of DNA

• Prophase – chromosomes visible

• Metaphase – lined up in the middle

• Anaphase – chromosomes move

• Telophase – two new nuclei form

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Mitosis Animation

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Some Mitosis Facts

• The two daughter cells made from mitosis are identical to each other and the parent cell.

• Mitosis happens most often in least specialized cells like early embryos.

Some Mitosis Facts

• Specialized cells like xylem, muscle, and nerve cells rarely, if ever, divide.

• Places of growth like root tips, bone marrow, and skin have cells that divide rapidly.

• A protein called cyclin regulates the cell cycle.

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Bellringer 10/29

• How is cytokinesis different in plant and animal cells?

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