Cell Growth and Division

Why do cells divide?

- large cells have difficulty transporting enough nutrients across their membran

Cells are limited in size by their SURFACE AREA and VOLUME ratio

 

CELL DIVISION - Process where a cell splits into two identical daughter cells. It occurs it two main phases.

-Mitosis - division of the nucleus
-Cytokinesis - division of the cytoplasm

CHROMOSOMES

-Made of DNA,containing the cell's genetic code
-Found in Nucleus
- Each chromosome has a matching pair, homologous pair
-Number depends on organism


CELL CYCLE - events cells go through as they grow and divide

Interphase (longest phase)

G1 - first growth (gap) phase
Synthesis - DNA makes a copy
G2 - second growth (gap) phase, preparing for mitosis

Mitosis - nucleus divides, ensuring each new cell has the exact number of chromosomes as parent

cell cycle

 

Mitosis

interphaseInterphase

(technically not part of mitosis, but it is included in the cell cycle)

Cell is in a resting phase, performing cell functions

DNA replicates (copies)

Organelles double in number, to prepare for division

 

prophaseProphase

1. chromosomes visible (chromatids)
2. centrioles migrate to the poles
3. nuclear membrane disappears
4. nucleolus disappears
5. spindle form

 

metaphaseMetaphase

Chromosomes line up along the equator

 

anaphaseAnaphase

Chromatids separate and move to opposite poles

 

 

telophaseTelophase

1. chromosomes disappear  (becoming chromatin)

2. nuclear membrane reforms

3. nucleoli reappears

4. spindle disappears

5. centrioles duplicate

Cytokinesis

cytokinesis

- division of the cytoplasm to form 2 new daughter cells

- organelles are divided

- daughter cells are genetically identical

- cells return to interphase

......cytokinesis takes two forms, depending on the cell....

Animal Cells - cell pinches inward and then splits into two

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Plants - a new cell wall (called the cell plate) forms between the two new cells

cytokinesis