Cell Division

Section 8.2

All cells are derived from the division of pre-existing cells

Cell division is the process by which cells produce offspring cells

Cell division in Prokaryotes

Binary fission- the division of a prokaryotic cell into 2 offspring cells

Cell division in Eukaryotes

Mitosis- results in new cells with genetic material that is identical to that of the original cell

Meiosis- reduces the chromosome number by half in new cells

The cell cycle

The repeating set of events that make up the life of a cell

Interphase- the time between cell divisions

M phase- mitosis

Cytokinesis- the division of the cytoplasm of the cell

Interphase

G1 phase-offspring cells grow to mature size

S phase- the cell’s DNA is copied

G2 phase- the time gap following the S phase and preceding cell division

G0 phase- cells do not copy their DNA and don’t prepare for cell division

Mitosis

Divided into 4 phases: prophase, metaphase, anaphase, and telophase

Prophase

First phase of mitosis

Centrosomes- appear next to the disappearing nucleus

Centrioles- found in animal cells

Spindle fibers- made of microtubles radiate from the centrosomes in preparation for mitosis

Mitotic spindle- equally divides the chromatids between the 2 offspring cells

Kinetochore fibers- attach to kinetochore

Kinetochore- disk-shaped protein

Polar fibers- extend across the dividing cell from centrosome to centrosome

Metaphase

Second phase of mitosis

The kinetochore fibers move the chromosomes to the center of the dividing cell

Anaphase

Third stage of mitosis

Chromatids of each chromosome separate at the centomere

Telophase

Fourth stage of mitosis

Spindle fibers disassemble

Chromosomes return to a less tightly coiled chromatin state

Cytokinesis

Cleavage furrow- pinches the cell into 2 cells (animal cells)

Cell plate- membrane-bound cell wall (plant cells)