The Cell Cycle and Mitosis

The Cell Cycle Cells reproduce by a cycle of growing and dividing called the cell cycle. Cell division prevents the cell from becoming too large. It also is the way the cell reproduces so that you grow and heal certain injuries.

Three Stages Interphase: the stage during which the cell grows, carries out cellular functions, and replicates. This is the longest stage in healthy cells. Mitosis: the stage of the cell cycle during which the cell’s nucleus and nuclear material divide. Cytokinesis: the method by which a cell’s cytoplasm divides, creating a new cell.

Interphase G1: Gap 1 phase, also called Growth 1 phase The cell is growing, performing normal cell functions, and preparing to replicate DNA.

Interphase S Phase: Synthesis phase. The cell copies its DNA in preparation for cell division. If DNA isn’t copied, cells would have half the number of chromosomes needed. Ex. 46 human chromosomes: 46/2= 23 chromosomes So, they duplicate: 46 x 2= 92 92/2= 46

Interphase G2: Gap 2 phase/ Growth 2 Phase. The cell prepares for the division of its nucleus.

Mitosis Four main stages Prophase Metaphase Anaphase Telophase PMAT!

Prophase The cell’s chromatin condenses. Chromatin is DNA wrapped around histones (proteins). Sister chromatids (identical halves of chromosomes) are attached at the centromere. Spindle fibers form from the centromere in the cytoplasm.

Prophase Sometimes these steps are called prometaphase. Nuclear envelope disintegrates. Spindle fibers attach to the sister chromatids.

Metaphase Sister chromatids are pulled along the spindle apparatus toward the center of the cell and align in the middle.

Anaphase Microtubules shorten, pulling sister chromatids apart and toward the poles of the cell.

Telophase The chromosomes arrive at the poles and begin to relax. Two new nuclear membranes begin to form and the nucleoli reappear. The spindle apparatus disassembles. The cell membrane develops a cleavage furrow.

Cytokinesis In animal cells, microfilaments constrict, or pinch, the cytoplasm. In plant cells, a new structure, called a cell plate, forms.