The Cell Cycle Objective 3.02 Mitosis related to asexual reproduction Order of the steps of mitosis with diagrams
The Basics… • Cells go through a process called the Cell Cycle, which is when a cell grows to it’s largest functioning size and then splits into two. • The original cell is called the parent cell. • The parent cell makes a copy of all the DNA inside the cell, called chromosomes, before it splits into two identical daughter cells. • This whole process takes about 20 hours.
Chromosomes • Are DNA • Are made up of two identical chromatids held together in the middle by a centromere. • Human somatic cells (body cells) have 46 chromosomes.
Chromosome Anatomy Sister Chromatid Centromere
Cell Cycle Continued… • The Cell Cycle is made up to 2 parts: • Interphase(Resting Phase) • Mitosis (Dividing Phase) • Occurs in somatic cells (Body Cells) • Does NOT occur in sex cells (egg, sperm)
Interphase • “Resting” phase (not really, it’s just not dividing!) • Parent cell is busy • G1: Growing & making organelles • S: Copying chromosomes (replication) • G2: Preparing for mitosis! • Similar to “pre-game”
Mitosis • Let’s start dividing! It happens in 4 stages: • Prophase: • Longest phase: 50% of the Cell Cycle (10 hours) • Chromosomes are visible • Nucleus begins to break apart & disappear. • Centrioles head to the poles (opposite sides) of the cell. • Remember: CentriOLES move to the pOLES
Mitosis • Metaphase: • The shortest phase of the Cell Cycle • Chromosomes line up down the middle of the cell (like stitching on a football) • The centromeres attach to the spindle fibers that run from one centriole to the other. • Remember : Middle = Meta!
Mitosis • Anaphase • Chromosomes begin to break apart • Remember: Apart = Ana! • Each ½ (Chromatid) begins to move toward the poles where the centrioles are.
Mitosis • Telophase: • Almost 2 new cells, but not quite…Cytoplasm is still connected. • 2 new nuclei begin to form • Cytokinesis: The separation of the cytoplasm between two daughter cells. They FINALLY separate!! Mitosis & Cytokinesis
Why Do Cells Divide? …and not just grow bigger? • If a cell becomes too big, it cannot support itself with it’s organelles. • In other words, it can’t keep up with demand! • Too difficult to move nutrients in and move waste out!