Mitosis Notes

Mitosis

Remember that mitosis is the name of the cell division that eukaryotic cells go through to create a new cell.

Mitosis is all about the division of the nucleus and there are names for each step that you will need to learn.

Cell Division

Mitosis- process of making new somatic (nonsex) cells like skin cells (clones)

Cell Cycle The Cell Cycle –

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

Mitosis is actually a name of one of the cell cycle steps usually referred to as the M phase.

Cell Cycle But most people call

the whole process Mitosis instead of the cell cycle, because it is a very important step.

Cell Division

Where do new cells come from?

All cells came from preexisting cells.

Steps of the Cell Cycle

1. Interphase – the longest phase, 80% of cells life is in this phase.

Steps of Interphase: G1 phase – growth of cell G0 phase – inactive stage. S phase – DNA is replicated (“S”

synthesis of DNA) G2 phase – growth of cell; prepares

for cell division

Steps of the Cell Cycle G0 phase – non dividing

state after the G1 phase; This is the only time a cell can

be stopped from dividing, and is why a cell spends the majority of its life in interphase.

Some cells in the human body like spinal cord cells get stuck in the G0 phase and never divides again, which is why spinal cord injuries don’t heal.

Cell Cycle

2. Mitosis – division of the nucleus; a continuous process divided into 4 phases

A. Prophase B. Metaphase C. Anaphase D. Telophase

M phase

G2 phase

S phase

G1 phase

Mitosis The following is what

happens during each phase of mitosis.

A. Prophase Chromosomes appear The nucleus begins to break

down Centrioles appear and

produce spindle fibers

Mitosis B. Metaphase Chromosomes align along

the equator of the cell Spindles Fibers move

chromosomes to the equator.

Spindle Fibers are attached to the centrioles (at poles) and connect to the centromeres on chromosomes.

Mitosis C. Anaphase Chromosomes are pulled

to the pole by the contraction of the spindle fibers

So, the sister chromatids are separated at the centromere

Mitosis D. Telophase The chromosomes begin to form a new nucleus. A new cell membrane/wall begins to form so the two cells can

separate If there is a cell wall what type of cell are we looking at?

Cell Cycle 3. Cytokinesis – division of the cytoplasm

The chromosomes start to uncoil and become less dense You now have two new genetically identical cells. Cytokinesis actually happens during Telophase, so you would

actually say Telophase/Cytokinesis.

Telophase/Cytokenisis

See cleavage in animal cells

See Cell plate form in plant cells.