The Cell Cycle

What is the life cycle of a cell? Is it like this? –Birth –Growth & development –Reproduction –Deterioration & Death Or is it like this? –Birth –Growth & development –Deterioration & Death

Cell Reproduction Organisms are not born with all the cells they will ever have. Organisms grow, and as they grow, their cells reproduce to make more cells. Prokaryotes & eukaryotes do this differently.

Prokaryotes: Cell Reproduction Prokaryotes (like bacteria) reproduce asexually. They split in two. This process is called binary fission.

Eukaryotes: Cell Reproduction Eukaryotes reproduce sexually and asexually. Reproductive cells undergo sexual reproduction. All other cells in the body, called somatic cells, undergo asexual reproduction to replace damaged cells and allow you to grow. This asexual reproduction is also called mitosis.

The Cell Cycle Mitosis is a small part of the cell cycle. Most of its life, the cell is not in mitosis, but in interphase. Both mitosis and interphase consist of several stages.

The Cell Cycle: Overview hill.com/sites/ /student_view0/chapter2/animation__how_the_cell_cycle_works.html What is cancer? Cancer is caused by mutations (change or damage) in the genes that regulate the cell cycle at its checkpoints. When these checkpoints fail, the result is uncontrolled cell division- also known as cancer.

Interphase Interphase has 3 stages- G 1, S, & G 2 During interphase, cells grow by making proteins, copies of their DNA, and extra organelles. (The S phase is when DNA replication occurs.)

Interphase: continued At the end of interphase, all of the DNA condenses into fibers in the nucleus called chromatin. The chromatin, in turn, will condense into thick segments called chromosomes in Prophase.

Chromosomes Each chromosome consists of 2 identical chromatids. These chromatids are held together by a centromere. The centromere will attach the chromatids to the spindle in mitosis. Later on, these chromatids will be separated.

Prophase In prophase, the chromosomes become clearly visible. The nuclear membrane disappears. Structures called centrioles move to opposite ends of the cell, and spindle fibers form between them.

Metaphase During metaphase, the chromosomes line up in the middle of the cell. Each chromosome is attached to a spindle fiber that ends at one of the centrioles.

Anaphase Anaphase is characterized by the chromosomes being pulled apart to opposite sides of the cell.

Telophase The last stage of mitosis is telophase. During telophase, nuclear membranes reform around the chromosomes at each end of the cell. Chromosomes unwind to chromatin and DNA.

Cytokinesis The very last part of cell reproduction is the division of cytoplasm. This is called cytokinesis. In plant cells, cytokinesis is complete when the cell plate has completely formed between both new nuclei, and two new daughter cells are made. In animal cells, a cleavage furrow is seen when the cell cytoplasm pinches inward to form the two new daughter cells.

Mitosis Animations

Mitosis Animations hill.com/sites/ /student_view0/chapter2/animation_ _mitosis_and_cytokinesis.html Game: