Chapter 8.1

Cell Division and Reproduction

Why do cells go through cell division?

• To grow– Organisms grow by ADDING more cells

• To replace dead cells– All cells will die so they need to be

replaced

• To replace damaged cells– Cells will be damaged by injury (cut)

Definition of Cell Division

• Cell division is the process of one cell dividing into two identical daughter cells

DNA - Hereditary Material

• DNA is stored in a eukaryotic cells nucleus – Plant cells– Animal cells

What is Chromatin?

• Loose (stringy) DNA in a cells nucleus is called chromatin

• DNA before cell division

• DNA ‘hanging out’

Chromosome doubles

• Chromatin condenses (shrinks up) and doubles just before cell division – This forms a

chromosome (X).

X X

What is a Chromosome?

• A chromosome is a structure made up of DNA and protein in the nucleus of a eukaryotic cell

Cell Cycle

• The cell cycle is the period of time from the beginning of one cell division to the beginning of the next.

• The cell cycle has 3 parts:– Interphase See cycle on page 155– Mitosis– Cytokinesis

1. Interphase

• First part of the cell cycle

• Time in between cell divisions– Cell is on vacation

• Longest phase. Most time is spent in interphase

• At end, chromatin (stringy) doubles into a chromosome (X)

Mitosis

• Second part of the cell cycle

• Makes 2 new identical nuclei

• Has 4 steps:– Prophase– Metaphase– Anaphase– Telophase

2. Prophase

• First step of mitosis

• Chromatin in nucleus coils into chromosomes (X’s)

• Nuclear membrane begins to disappear

3. Metaphase

• Second step of mitosis

• Chromosomes line up in the middle of the cell

• Spindle fibers attach to the chromosomes

4. Anaphase

• Third step of mitosis

• Chromosomes separate and begin to move to opposite ends of the cell

5. Telophase

• Final step of mitosis

• Two new nuclei form around the separated chromosomes

• Chromosomes unwind to form chromatin

• Mitosis ends

6. Cytokinesis

• Final part of the cell cycle

• Makes 2 new identical daughter cells

• Shortest phase

• END of the cell cycle

Cell Cycle

• Interphase

• Prophase

• Metaphase Mitosis

• Anaphase

• Telophase

• Cytokinesis

Cell Cycle Mnemonic• Write a mnemonic for cell division• (Ex. King Henry Died By Drinking

Chocolate Milk.)• I• P• M Add a COLORED • A picture• T• C

Cell Cycle Mnemonic

• I

• Played

• Music

• At

• The

• Concert