Mitosis

A Form of Cell Division

"Every cell comes from a cell..." (R. Virchow)

I. Cell Size

A. Cells grow until they are too big to take in sufficient nutrients or get rid of wastes.

B. The cell will maintain itself or will divide into two smaller cells.

C. The process of cell growth and cell division is called the cell cycle.

The Cell • The eukaryotic cell has a nucleus in which

there chromosomes.

• The chromosomes carry genetic information in the form of DNA.

• During growth and maintenance the chromosomes are spread out in the nucleus in a

form called

chromatin.

Check Point• 1. What is the process of cell growth and

division called?– The cell cycle

• 2. Cell theory states that all living cells come form___________.– Existing cells

• 3. What carries genetic information in the form of DNA?– Chromosomes

II. Interphase

A. Most of the life of the cell is spent in Interphase, a period of growth and maintenance.

B. If the cell is a type that divides, then it will go through a process of cell division called mitosis.

Interphase

Check point

• What two main things happen during interphase?– Growth and DNA replication

III. Why Divide?

A. Single-celled organisms divide to reproduce.

B. Cell division in multicellular organisms enables the organism to grow larger while the cells remain small. 

C. A large surface:volume ratio is due to small cell size. This allows sufficient food to enter, wastes to leave, and gases to be exchanged.

IV. What is Mitosis?

A. Mitosis is the division of the mature parent (mother) cell into two smaller daughter cells.

B. The daughter cells are identical to the parent cell.

C. There are four stages called prophase, metaphase, anaphase, and telophase.

Check Point

• How many daughter cells does mitosis produce?

V. Which Cells Divide?A. Cells that divide constantly and

rapidly in animals:

1. Skin cells

2. Sperm cells

3. Bone marrow cells

B. Cells that divide constantly and rapidly in plants:

1. Root tip cells

2. Phloem cells

3. Meristematic tissue for growth and replacement

VI. MitosisA. Cells divide to make more cells.

B. While all the other organelles can be randomly separated into the daughter cells, the chromosomes must be precisely divided so that each daughter cell gets exactly the same DNA.

Maintaining cell identity

• Human body cells have 46 chromosomes, 23 from each parent.

• Every body cell has the same 46 chromosomes • Each species has a characteristic number of

chromosomes: corn has 20, house flies have 10, chimpanzees have 48.

• After cell division (mitosis), the resulting daughter cells must have the same number of chromosomes as the parent cell.

Chromosomes

• The essential part of a chromosome is a single very long strand of DNA. This DNA contains all the genetic information for creating and running the organism.

VII. The Steps of Mitosis

A. In the parent cell the DNA in the chromosomes is copied during Interphase.

B. The four phases of mitosis divide these copied chromosomes so that each daughter cell will receive one full set of the chromosomes.

Check point

• How many chromosomes do we get from each parent?– 23

Mitosis in Plant Cells

Prophase

Metaphase

Anaphase

Telophase

Mitosis in Animal Cells

Prophase

Metaphase

Anaphase

Telophase

Class Activity