300 MILLION CELLS DIE IN THE HUMAN BODY

EVERY MINUTE

TODAY’S SCIENCE SMILE

Mitosis

Mitosis

Mitosis takes place when a parent cell divides into 2 identical daughter cells.

Before mitosis takes place, DNA must be duplicated so that the daughter cell receives an exact copy from the parent cell.

Passing on genetic information through cell division is called genetic continuity.

Mitosis takes place in somatic (body) cells.

WHO REMEMBERS???!!

WHY DO CELLS DIVIDE?

THE THREE REASONS WE LOOKED AT…

GROWTHREPAIR

REPRODUCTION

Overview on why they divide?

Cells must divide in order to function properly.

If cells become too large, the following problems arise:

The cell cannot take in enough nutrients to satisfy the cell’s requirements.

The nucleus cannot control the activities of a cell that is too large

The Cell Cycle

The cells spend most of their time growing, in a phase called Interphase.

When a cell needs to divide, it will enter the Mitotic phase.

The Cell Cycle is divided into 4 stages: G1 Phase – Cell growth S Phase – DNA is replicated G2 Phase – Cell prepares for mitosis M Phase (Cell division ) – cell undergoes mitosis

The Cell Cycle

Interphase

Interphase:Chromosomes are not readily visible

but appear as an irregular network of strands called chromatin

Nucleus is visibleNuclear membrane is visibleNucleoli are visible

Interphase

THERE ARE FOUR STAGES IN MITOSIS

THIS IS WHERE CELL DIVISION TAKES PLACE!!!

PAGE IN YOUR TEXTBOOK!!

Mitosis

First Stage - Prophase

Prophase:Centrioles move to opposite poles of the cellChromatin condenses into short, thick chromosomesThe replicated chromosomes become clearly visible and

are held together at a single point called a centromereEach identical strand is called a chromatidThe nuclear membrane breaks down The nucleoli disappearSpindle fibres begin to form around the centriolesThe spindle fibres attach to the centriolesThe chromosomes begin to move into the middle of the

cell

Prophase

Second Stage - Metaphase

Metaphase:Chromosomes line up at the equator of the

cell in a specific wayThis area is sometimes called the metaphase

plate

Metaphase

Third Stage - Anaphase

Anaphase:Chromosomes begin to separate into

chromatids The chromatids are held at the centromere by

the spindle fibres Each chromatid is pulled towards opposite

poles of the cell Anaphase ends when a complete set of

chromatids arrives at each of the poles

Anaphase

Fourth Stage - Telophase

Telophase:The daughter cells return to interphase

conditionsThe nuclear membrane reformsNucleoli reappearChromosomes elongate by uncoiling and

become chromatin once againThe spindle fibres and centrioles disappearTwo nuclei are visible within a single cell

Telophase

End of Telophase - Cytokinesis

Cytokinesis:In animal cells, the cell membrane pinches inwards at

the equator, producing a furrowThe furrow deepens until two separate cells are

produced, each with their own nucleus and cytoplasmThe parent cell’s organelles are distributed to each of

the daughter cellsIn plant cells, a cell plate forms across the equator of

the cell (begins in late anaphase)Cellulose is added and eventually, a new cell wall

divides the parent cell into two daughter cells (see text pg 164)

Now there are two cells!!!

Easy ways to memorize this:

Use a mnemonic:

Interesting People MakeA Terrific Conversation

I Played Myself A Tune Clearly

P

Use a visual:

“PMAT”

P

Or your hands!!!

Now watch the Animations

http://www.cellsalive.com/mitosis.htmhttp://highered.mcgraw-hill.com/sites/007249

5855/student_view0/chapter2/animation__mitosis_and_cytokinesis.html

NAME THE STAGES…

Using your handout, see if you can identify the stages of mitosis…….

FILL IN THE BLANKS

Use the words at the bottom of the handout too complete the story of mitosis.

Mitosis Matching

Step 1Using the mitosis handout. Cut out the

images at the bottom of the sheet.Step 2 Match each image with the correct name in

the circle above.

I will be walking around to help!

Homework Text: Read pgs ___________________ Complete questions _____________________