Cell Division The Cell Cycle and Mitosis Why

Cell Division The 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 copied 2. Cells begin to divide 3. 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. Mitosis 2. 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 G 1, S and G 2 phases

Interphase

Interphase: G 1, S, G 2 • G 1 (Gap 1)- Cells grow to mature size • S (Synthesis)- DNA is copied • G 2 (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. anaphase 2. 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

Telophase

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