Download Cell Division and the Nucleus

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.
o ______________ - 95% of the time the genetic
material appear like this.
 “Spaghetti like”, uncoiled, long, thin and stringy
 Found during interphase
o ______________ - 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
o Prophase, Metaphase, Anaphase, Telophase (I-PMAT)
Stage 1: INTERPHASE (inter = between…stage between mitosis)
 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.
2. What occurs during cytokinesis?
3. How many phases are there in the cell cycle? _____ How many phases of mitosis
are there? _____
4. How can you remember the order of the cell cycle? ______________________
5. When one parent cell divides it makes _________ exact copies of itself called
____________________ cells.
6. Why is mitosis important?
7. Why is it necessary to duplicate the nuclear material before mitosis occurs?
8. The only cells in a human body that are not formed through mitosis are
____________ cells.
9. A human skin cell contains 46 chromosomes, after mitosis occurs how many
chromosomes would there be in each of the two cells? ___________
10.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.