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
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?