Cell Division and the Cell Cycle

The Cell Theory – Things to Remember!

1. ______

2. ______

3. ______

Functions of Cell Division

Healing & Tissue Repair

  • ______of cells in our bodies _____ or are ______every second and they need to be ______, otherwise we would disappear!
  • E.g.

Growth and Development

  • Cells ______so that we can ______.
  • Single cells get ______and eventually divide.
  • Materials such as ______and ______are more easily controlled in smaller cells.
  • Diffusion and Osmosis are vital to cell survival!
  • E.g.

Reproduction

  • Enables organisms to ______, otherwise ______would die out.
  • Applies to ______(body cells, bacteria, amoeba) & ______organisms (sex cells) through different processes of cell division.
  • E.g.

Sexual vs Asexual Reproduction

Cell Division and the Nucleus

  • The nucleus is the “______” of the cell. It contains ______, which are made of DNA and proteins.
  • When a cell divides, the ______material must ______and divide as well.
  • Each chromosome is a long DNA molecule typically containing 1000’s of genes.
  • ______- 95% of the time the genetic material appear like this.
  • “Spaghetti like”, uncoiled, long, thin and stringy
  • Found during interphase
  • ______- 5% will appear like this in an actively growing cell.
  • Coiled, short & thick, can be seen under the microscope
  • Found during Mitosis (cell division)

Variation in Genetic Material

Depending on the stage of the Cell Cycle, chromosomes will have different appearances and different names.

The Cell Cycle: Interphase + Cell Division

Interphase

  • ______

Cell Division

  • Includes both ______(nuclear division) & ______(division of organelles and cytoplasm)
  • There are four phases of Mitosis
  • Prophase, Metaphase, Anaphase, Telophase (I-PMAT)

Stage 1: INTERPHASE (inter = between…stage between mitosis)





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  • Cell ______& ______itself for mitosis by building ______.
  • ______genetic material called ______, now double stranded.
  • ______are also replicated, more organelles form.

Stage 2: PROPHASE (pro = start…first stage of mitosis)

/
  • Genetic material now called ______
  • Chromosomes shorten & thicken, now visible in light microscope
  • Nuclear membrane & nucleolus breakdown, freeing the chromosomes
  • Centrioles move away from each other and form ______

Stage 3: METAPHASE (meta = middle…middle stage of the cycle)


/
  • ______membrane has disappeared.
  • Centrioles have reached ______poles.
  • Chromosomes line up in the middle of the cell or ______.
  • They are attached to the spindle fibres by their ______.

Stage 4: ANAPHASE (ana = backwards…daughter chromosomes pulled back)

/
  • Spindle fibres shorten to pull and separate duplicated chromosomes to opposite poles of the daughter cells.
  • The chromosomes are now referred to as ______chromosomes.

Stage 5: TELOPHASE (telo = end…end of mitosis) & Stage 6: Cytokinesis

/
  • Daughter chromosomes have reached opposite poles and begin to uncoil.
  • Nuclear membrane and nucleolus reform.
  • Spindle fibres disappear.
  • Daughter Cells are genetically identical.
  • Cytokinesis begins.

Stage 6: CYTOKINESIS (Animal vs Plant)

And….. It All Begins Again!!

  • Two new “daughter” cells in interphase.

Discussion Questions

  1. Define the terms chromatin, chromosome, chromatid and centromere. Use diagrams to distinguish between these terms.
  1. What occurs during cytokinesis?
  1. How many phases are there in the cell cycle? _____ How many phases of mitosis are there? _____
  2. How can you remember the order of the cell cycle? ______
  3. When one parent cell divides it makes ______exact copies of itself called ______cells.
  4. Why is mitosis important?
  5. Why is it necessary to duplicate the nuclear material before mitosis occurs?
  6. The only cells in a human body that are not formed through mitosis are ______cells.
  7. A human skin cell contains 46 chromosomes, after mitosis occurs how many chromosomes would there be in each of the two cells? ______
  8. X-rays and other forms of radiation can break chromosomes apart. Doctors and dentists ask women whether they are pregnant before taking X-rays. Why don’t they want to X-ray pregnant women? Explain.