The cell cycle and mitosis
Mar 27, 2015
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?