Cell Growth and Division Chapter 5

If you cut your finger, your cells grow and divide to make more cells. This is how your finger heals.

Cells grow and divide in a regular pattern, or cycle that is referred to as the .....
The Cell Cycle 5.1

The cell cycle has 4 main stages:

Gap 1 (G1): During this stage the cell grows in size and organelles get replicated. The cell spends 8-10 hrs in this stage (most of its time is spent here).

Synthesis (S): During this stage the cell synthesizes (makes) duplicate copies of its DNA. The cell spends 6-8 hrs in this stage.

Gap 2 (G2): During this stage the cell checks for errors in DNA synthesis and begins to grow in size preparing itself for cellular division. The cell spends 4-6 hrs in this stage.

These Three Stages Are Known As Interphase

















Mitosis (Mitotic Phase) (M): During this stage the cell prepares to divides into two cells through the process of Prophase, Metaphase, Anaphase, and Telophase. The cell spends 3 hrs to complete this stage.


Cytokinesis is the process of the cell completely dividing into two cells.

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Section 5.2 The Stages of Mitosis:

Your nucleus commands cells to divide but before it divides it must first duplicate and condense its DNA into CHROMOSOMES.....

If you stretched the DNA in one cell all the way out, it 

would be about 2m long and all the DNA in all your cells 

put together would be about twice the diameter of the 

Solar System.

DNA Condensing Video






Lets understand the structure of a chromosome (condensed form of DNA)....

Chromosome Structure:

• A chromosome is one long continuous thread of DNA. 

• DNA wraps around proteins called histones. 

• DNA and histones form chromatin, which looks like spaghetti, during interphase. 

• Chromosomes condense tightly for mitosis

 because they are duplicated, they look like an X.

Lets examine the phases of cellular division known as Mitosis....

1. interphase: copies DNA, grows, duplicates organelles

2. prophase: chromosomes condense, nuclear envelope breaks down, spindle fibers form

3. metaphase: spindle fibers align chromosomes along the cell equator

4. anaphase: chromatids separate to opposite sides of cell

5. telophase: nuclear membranes start to form around chromosomes, chromosomes begin to uncoil, spindle fibers fall apart

6. cytokinesis: divides the cytoplasm between two daughter cells

Prophase: 



Metaphase: 



Anaphase:



Telophase:




Cytokinesis: 

BrainPop Mitosis Video


Lets assess your knowledge....

Mitosis Dance


Section 5.3 Regulation of Cells:


If the cell goes out of control, cancer can result. Cancer is uncontrolled/unregulated cell division.



Just as cells need to grow and divide, other cells need to 

die. Internal or external signals can start an orderly 

process of cell death. The cell is broken down and its 

parts are reused in building other molecules. This 

process of programmed cell death is called apoptosis 

Apoptosis Video
 


Cancer Animation

Section 5.4 Asexual Reproduction: 










Advantages of Asexual vs Sexual Reproduction:
Quick
One parent needed
All good characteristics are passed on


Disadvantages:

No variation (all look the same)

Offspring inherit bad traits

Adaptation to environment is unlikely





Section 5.5 Multicellular Life: 

Cell differentiation- not all cells look alike 

or perform the same function but at one 

point they all had a choice. 




What Are Stem Cells?