Cell DivisionThe Cell Cycle and Mitosis
Why do cells divide?
•Growth
•Repair
•Reproduction
Chromosomes
• Carry genetic information from one generation of cells to the next
• Not visible in cells except in cell division
Cell Division
• Process by which a cell divides into two daughter cells
• Before division, the cell replicates all its DNA
• Each daughter cell will get one complete set of genetic information
Cell Division- Prokaryotes• Binary fission:
asexual cell division of prokaryotes that produces identical offspring
• Three Steps:1. DNA is copied2. Cells begin to divide3. Two identical cells
Binary Fission
Bacterial cell dividing by binary fission
E. Coli dividing by binary fission
Cell Division- Eukaryotes
• Nucleus first and then the Cytoplasm divides
• There are two kinds:1. Mitosis2. Meiosis
• Cell cycle: set of events making up the life of a cell; composed of interphase and cell division
The Cell Cycle
Interphase• The time between cell
divisions where the cell spends most of its life
• Cell is in a resting phase, performing cell functions
• Composed of G1, S and G2 phases
Interphase
Interphase: G1, S, G2
•G1 (Gap 1)- Cells grow to mature size
•S (Synthesis)- DNA is copied
•G2 (Gap 2)- cell organelles grow and prepare for division
Mitosis• Division of nucleus
• Daughter Cells wind up with the same # of chromosomes
• There are 4 phases:1. prophase 3. anaphase2. metaphase 4. telophase
Prophase• Chromosomes become visible
• Centrioles separate and move to opposite sides of nucleus
• Spindle fibers form
Prophase• Nucleolus disappears
• Nuclear Envelope breaks down and disappear
• Prophase is the longest phase of cell division
Prophase
Metaphase• Chromosomes line up along the
equatorial plate (middle of the cell)
• Chromosomes connect to spindle fibers at centromere
• Metaphase is the shortest phase
Metaphase
Anaphase
• Sister chromatids separate and move to opposite poles
• When chromatids separate, they are considered individual chromosomes.
Anaphase
Telophase• Nuclear envelope forms around each
group of chromosomes
• Chromosomes relax back into chromatin
• Spindle fibers disassemble.
• Cytokinesis begins
Cytokinesis• The process by which the
cytoplasm divides and one cell becomes two individual cells
• Different in plants and animals– Animals- cell pinches inward to
form a cleavage furrow– Plants- a cell plate forms between
the two new cells forming a cell wall
Cytokinesis- Animal Cell
Cytokinesis- Plant Cell
Cytokinesis- Plant vs. Animal
