The Cell Cycle: Mitosis Notes

Facts Somatic cells – “soma” means body Body cells each contain the same number of chromosomes How many chromosomes do human body cells have? 46

Chromosome = cell structure that contains the genetic material in the form of DNA. This is located inside the nucleus. Centromere Chromatid Sister Chromatid

Centromere = cell structure that joins two chromatids together to form a sister chromatid. Chromatid = one copy of the original chromosome. Sister chromatid = identical halves of the duplicated parent (original) chromosome formed during interphase.

Interphase The time between the formation of the cell and the next mitosis Duplication of genetic material Produces organelles Assembles structures needed for mitosis

Phases of Mitosis Prophase – this is the first step of mitosis and it lasts the longest. Usually 60% of the total time for mitosis. Chromosomes coil up into short rods Nucleolus and nuclear membrane disappear Spindle fibers form between centrioles Centrioles move to opposite ends of the cell

Metaphase – second phase of mitosis Meta = middle Centromeres of chromosomes attach to spindle fibers Chromosomes are arranged along the center line of the cell

Anaphase – third phase of mitosis Centromeres separate Chromatids separate and become separate chromosomes again Spindle fibers pull chromosomes apart to opposite ends of the cell Plasma membrane begins to pinch in the middle

Telophase – final stage of mitosis Nuclear membrane forms around each set of chromosomes Nucleolus and plasma membrane re-form

Cytokinesis – the division of cytoplasm Animal cells – plasma membrane pinches in at the end of telophase and two new cells separate. Plant cells – since plant cells have a rigid cell wall, the plasma membrane can’t just pinch in. So, a cell plate forms across the middle of the cell to separate the two cells into separate cells.