The cell cycle and mitosis

• Cells constantly reproduce exact duplicates of themselves. Why?

• Replacement

• Repair

• Growth

• Cells must make an exact copy of their DNA

• DNA is the blueprint of the cell and is found in the nucleus

• Cell growth and division happens in a series of recognizable steps called the Cell Cycle

• Rephrase: what is the cell cycle?

• Cell cycle has three phases

• 1. Interphase– Cell growth– DNA replication

occurs

• 2. Mitosis– Nuclear division– 2 daughter cells

formed, each has identical DNA

• 3. Cytokinesis– 2 identical cells

Cell cycle

Interphase(DNA

duplication)

Mitosis(Nuclear Division)

Cytokinesis(cytoplasm

division)

• DNA forms chromosomes-

• For most of the cell’s life, DNA is arranged “loosely” in the form of chromatin

• During mitosis DNA condenses into chromosomes

Interphase

• Longest phase

• Cell grows

• Chromosomes are duplicated- each duplicate is called a sister chromatid

Prophase

• Nuclear envelope breaks down

• Sister chromatids joined at centromere

• Centrioles move to opposite ends and the spindle fibers form between them

Metaphase

• Short• Spindle fibers attach

to centromere• Sister chromatids line

up along midline

Anaphase

• Sister chromatids are pulled apart by the spindle fibers

Telophase

• Final phase of mitosis- opposite of prophase

• Chromatids reach opposite poles

• Nuclear envelope reforms

• Chromosomes unwind

Cytokinesis

• Cytoplasm division

• Cytokinesis differs between plants and animals- why?