The cell cycle and mitosis. Cells constantly reproduce exact duplicates of themselves. Why?...
Transcript of The cell cycle and mitosis. Cells constantly reproduce exact duplicates of themselves. Why?...
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?