The cell cycle Interphase and Mitosis Cell Cycle

The cell cycle Interphase and Mitosis

Cell Cycle n Interphase—time when cell is NOT dividing – Growth (G 1) – Replication of DNA (S) – Preparation for next division (G 2)

MITOSIS n Many kinds of cells constantly grow and reproduce n Cell reproduction has two portions – Division of the nucleus (mitosis) – Division of the cytoplasm (cytokinesis) n Though we look at mitosis in “stages” it is a continuous process with no marked change indicating that one phase is over and the next has begun

Prophase n n Chromosomes become visible Centrioles copy and begin movement to opposite poles The “spindle” begins forming The nucleus begins to break down (nuclear envelope)

Metaphase Chromosomes line up at the center of the cell (“equator”) n Spindle fibers are attached to centromeres of chromosomes n

Anaphase n Chromatids separate and are pulled to opposite sides (“poles”) of the cell by the fibers attached to centrioles

Telophase n Opposites of prophase – Chromosomes unwind are no longer visible – Nuclear envelopes begin to form – Spindle apparatus is disappearing

Cytokinesis n The cell membrane then pinches together by microfilaments and microtubules pinching together between the two forming cells n The new cells are genetically identical

Cell differentiation n Process by which cells develop different characteristics in structure and function n Figure 3. 20