Binary Fission and Mitosis Cell Division in Prokaryotes

Binary Fission and Mitosis

Cell Division in Prokaryotes • Binary Fission • A form of asexual reproduction: • Reproduction that has only one parent • Steps involved: • The DNA replicates • The cell gets longer, causing the chromosomes to separate • The cell wall and membrane grow down the middle of the cell, separating the 2 sides • You end up with 2 daughter cells that are identical

Binary Fission

Cell Division in Eukaryotes • There are two kinds of cell division in eukaryotes: 1. Mitosis is division that results in new cells with genetic material that is identical to the genetic material in the original cell 2. Meiosis occurs during the formation of gametes

The Cell Cycle • The cell cycle is the repeating set of events in the life of a cell • It consists of cell division and interphase • Cell division in eukaryotes includes nuclear division, called mitosis, and the division of cytoplasm called cytokinesis

Interphase • Interphase is the time between cell divisions • It consists of: • Growth (G 1 phase): The offspring cell grows to mature size • DNA replication (S phase): DNA is synthesized (copied) • Preparation for cell division (G 2 phase): this is just a time gap after the DNA is copied

Mitosis • Mitosis is the division of the nucleus during cell division to make a DIPLOID cell • It happens in 4 stages: • Prophase • Metaphase • Anaphase • Telophase • Mitosis results in 2 offspring cells that are genetically identical to the original cell. • Mitosis is followed immediately by cytokinesis, which divides the cytoplasm. • These two stages together are referred to as “M Phase” of the cell cycle.

Prophase • The chromatids shorten and coils into rod-shapes chromosomes • The nucleolus and the nuclear membrane disappear • Centrosomes appear next to the disappearing nucleus • Spindle fibers made of microtubules form and radiate from the centrosomes • This collection of spindle fibers is called the mitotic spindle • It helps divide chromatids so each cell gets one of the pair

Prophase Mitotic Spindle Centrosomes Spindle Fibers Nucleus (disappearing)

Metaphase • During this phase the chromosomes are much more visible • Chromosomes move to center of cell and line up single file Chromosomes Spindle Fibers

Anaphase • The chromatids of each chromosome separate at the centromere • They slowly move, centromere first, to the opposite sides of the cell • Once they are separated, they are considered individual chromosomes. Chromosome Spindle Fibers Centromere

Telophase • The chromosomes reach the opposite ends of the cell • Spindle fibers disappear. • The chromosomes unwind back into chromatin • A nuclear envelope forms around each set of chromosomes • A nucleolus forms in each of the newly forming cells

Cytokinesis • Cytokinesis is the process by which the cytoplasm divides • Cytokinesis begins as the cell membrane pinches inward, near the middle of the cell. • This pinching inward is called a cleavage furrow • In plant cells, a cell plate made from particles from golgi separates the dividing cell into 2 cells