Warm-up: Why do cells divide? HW: Enter Date Aim: MITOSIS Regents Biology

Where it all began… You started as a cell smaller than a period at the end of a sentence… Regents Biology

Getting from there to here… Going from egg to baby…. the original fertilized egg has to divide… and divide… Regents Biology

Why do cells divide… for reproduction for growth & development one celled organisms (clones) for growth & development from fertilized egg to multi-celled organism for repair replace cells that die from normal wear & tear or from injury amoeba starfish Unicellular organisms Cell division = reproduction Reproduces entire organism& increase population Multicellular organisms Cell division provides for growth & development in a multicellular organism that begins as a fertilized egg Also use cell division to repair & renew cells that die from normal wear & tear or accidents Regents Biology

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Dividing cells… What has to be copied DNA organelles cell membrane lots of other molecules enzymes plant cell animal cell Regents Biology

What is Mitosis? Mitosis is the division of the cell’s nucleus. This process makes two identical cells. http://vimeo.com/8333643

Steps of Mitosis The steps involved in mitosis include: 1. Interphase 2. Prophase 3. Metaphase 4. Anaphase 5. Telophase 6. Cyntokinesis

http://www.ehow.com/vi deo_4984775_what- interphase.html During interphase, the cell grows and prepares for cell division. It is divided into three phases: 1. G1 phase 2. S phase 3. G2 phase

G1 Phase During this phase, cells do most of their growing. They increase in size and synthesize new proteins and organelles.

S Phase During this phase, chromosomes are replicated and the synthesis of DNA molecules takes place.

G2 Phase During this phase, all the rest of the organelles and molecules needed for division are produced. This is a very short phase. Once this phase is complete, the cell enters the M phase. (M stands for Mitosis)

Mitosis: Dividing DNA & cells Stage 1: cell copies DNA Copy DNA! DNA cell nucleus (interphase) Regents Biology

Mitosis: Dividing DNA & cells Stage 2: DNA winds into chromosomes DNA is wound up into chromosomes to keep it organized duplicated chromosomes Wind up! cell nucleus (prophase) Regents Biology

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Mitosis: Dividing DNA & cells Stage 3: Chromosomes line up chromosomes line up in middle attached to protein “cables” that will help them move Line up! duplicated chromosomes lined up in middle of cell (metaphase) Regents Biology

Mitosis: Dividing DNA & cells Stage 4: Chromosomes separate chromosomes split, separating pairs start moving to opposite ends Separate! chromosomes split & move to opposite ends (anaphase) Regents Biology

Mitosis: Dividing DNA & cells Stage 5: Cell starts to divide cells start to divide nucleus forms again Divide! (telophase) Regents Biology

Mitosis: Dividing DNA & cells Stage 6: DNA unwinds again cells separate now they can do their every day jobs Bye Bye! (cytokinesis) Regents Biology

Cytokinesis in Plants In plant cells, the only difference is that a cell plate forms between the two cells. This cell plate develops into a cell membrane and the cells eventually split.

New “daughter” cells Get 2 exact copies of original cells same DNA “clones” Regents Biology

Mitosis in whitefish embryo Regents Biology

Mitosis in plant cell Regents Biology

Overview of mitosis Copy DNA Wind Up Bye-Bye! Line Up Separate Divide Regents Biology Line Up Separate Divide