CELL GROWTH AND DIVISION

*How did I grow taller?

*How are my worn out cells replaced?

*How do I heal from injuries?

The answer is….Cellular Reproduction or Mitosis

THE CELL CYCLE:

*Cells go through cycles during their lifetime.

*Cells spend MOST of their time in a stage of growth and development called Interphase

 

Interphase

Cells grow in size and number of

organelles. This is the Growth and

Development stage.

 

 

Chromosome Replication

 Cell Reproduction (Mitosis)

 

  Prepare for cell reproduction (Mitosis)

Mitosis1. Type of cell division when chromosomes are duplicated and then separate into two identical and complete sets to be passed to each of the two daughter cells.

For example in humans, body cells have 46 chromosomes. After mitosis, each of the

two new identical daughter cells will have 46 chromosomes.

2. In this type of cell division, the hereditary information is identical in all the cells that result.

3. Responsible for growth, maintenance and repair.

4. In some one-celled organisms, asexual reproduction is achieved through mitosis.

5. Cancers are a result of abnormal cell division.

Meiosis

1. Responsible for producing egg and sperm

 

2. The resulting daughter cells contain one-half the hereditary information.

For example, in humans, each sperm or egg would contain 23 chromosomes.

Key wordsCell membrane: Controls what enters and leaves the cell

Nuclear membrane: Controls what enters and leaves the nucleus

Chromosomes: Contains the DNA

Centromere: Holds the Chromosomes together

Centriols: Pulls the chromosomes apart

CELL CYCLE:

During interphase chromosomes are copied (the number doubles). Chromosomes appear as threadlike coils (chromatin) at the start, but each chromosome and its copy change to sister chromatids at the end of this phase.

MITOSIS BEGINS: Prophase

During Prophase, nuclear membrane breaks apart. Centrioles begin to move to opposite ends of the cell. Spindle fibers form between the centrioles (at the poles of the cell).

Metaphase

During Metaphase chromosomes line up at the middle of the cell and attach to the spindle fibers.

Anaphase

During Anaphase chromosomes are separated and are pulled to the opposite sides of the cell.

Telophase

During Telophase, nuclear membrane reforms around two sets of chromosomes.

MITOSIS ENDS

Final stage of the cell cycle is Cytokinesis, or the splitting of two cells. Each new identical cell has its own nucleus with identical chromosomes.

 In animal cells, the cell membrane moves inward and pinches together.

In plant cells, a cell plate forms from the center outward until a cell wall is made.

RESULT OF A MITOSIS DIVISION:

*Number of chromosomes in each of the two resulting daughter cells is the same as the amount of chromosomes in the original parent cell.

*For example: In fruit flies the parent cell has 8 chromosomes. After mitosis, each new daughter cell has 8 chromosomes.