Transcript Cell Cycle
Cell Cycle Cell Cycle • The cell Cycle is a series of steps in which a cell is created, grows, performs its function, copies its DNA, and creates a new cell that is identical to itself. Cell Cycle G1 • G1 is the first stage of a new cells life. • During G1 the cell grows and performs its job. • G1 is the longest part of the cell cycle in most eukaryotic cells. Cell Cycle S • S phase is the second part of the cell cycle, and takes place after G1 • During S phase the cell copies its DNA • After S phase the cell has two copies of each gene. • The cell prepares for G2 Cell Cycle G2 • During G2 the cell goes through a second growth stage. • Preparations are made for gene separation. • Mitochondria and other organelles replicate, chromosomes condense, and microtubules begin to assemble at a spindle. Cell Cycle M (mitosis) • During M phase, the microtubular apparatus assembles and binds to the chromosomes, and moves the sister chromatids apart. • Mitosis consists of several steps that are essential for the creation of new daughter cells. Cell Cycle Cytokinesis • The cytoplasm divides creating two new daughter cells. Duration of the cell cycle • The time needed for the completion of the cell cycle varies from one organism to the next. • Cells in growing embryos can complete their cell cycle in under 20 minutes • Most cells in adult organisms take about 24 hours to complete the cell cycle. Mitosis Cell Division • Mitosis is a series of four steps in which one cell divides and two new identical cells are created. • The steps of mitosis are as follows. – Prophase – Metaphase – Anaphase – Telophase Mitosis Prophase • • • • The nuclear membrane dissolves. The nucleolus disappears Chromosomes form Spindles begin to form between the centrioles Super coiling of DNA Mitosis Prophase • Centrioles act as anchors for the mitotic spindle apparatus. • One side of the centriole connects to the cell membrane, & the other to the chromosmes. Mitosis Prophase • Spindle apparatus Mitosis Metaphase • The chromosomes line up along the equator of the cell. • Homologous chromosomes pair up. Mitosis Metaphase • Homologous Chromosomes are a pair of the same chromosome. Mitosis Anaphase • Sister chromatids are pulled to opposite sides of the cell. Mitosis Anaphase • Sister chromatids are identical copies of genes that are connected at the centromere of a chromosome. Mitosis Telophase • A nuclear membrane forms around each set of chromosomes. • Chromosomes unwind back to strands of DNA. • The cell membrane pinches in. • Mitosis is complete Cytokinesis • In cells that do not have a cell wall, the cell completely separates and two daughter cells are formed. Cytokinesis • In cells with a cell wall, a cell plate forms separating the two cells.