CELL DIVISION IS PART OF THE CELL CYCLE A CYCLE IS ANY ACTIVITY THAT REGULARLY REPEATS. CELL CYCLE INCLUDES INTERPHASE & CELL DIVISION (MITOSIS & CYTOKINESIS) All living things live, grow, reproduce & die in a life cycle. Cell Cycle = normal sequence of development & division of a cell. 2 main phases, INTERPHASE (cell carries out its functions) & CELL DIVISION (mitosis & cytokinesis) All cells divide, but only eukaryotes (with nucleus) use mitosis. Each phase in cycle takes certain amount of time from hours to days or years, depending on cell type. CELL DIVISION MAKES 2 GENETICALLY IDENTICAL CELLS
INTERPHASE & CELL DIVISION Mitosis is part of cell division where nucleus divides (not occur in prokaryotes- only 1 chromosome & no nucleus) CYTOKINESIS: division of the parent cell’s cytoplasm (right after mitosis) 2 identical “daughter” cells form with complete set of DNA from parent cell. Cell cycle has 2 parts (interphase & cell division) INTERPHASE: cell is not dividing, but much of cell’s activity occurs here. Cell grows to 2X original size & does its normal life activities. DNA gets copied here to prepare for cell division
CELL DIVISION MAKES 2 IDENTICAL CELLS Daughter cells are genetically identical to each other & parent cell (which no longer exists) Will perform same functions. Mitosis has 4 phases: prophase, metaphase anaphase & telophase PROPHASE: nuclear membrane disappears, chromatin coils to chromosomes METAPHASE: chromosomes line up in middle of cell (chromatids attached by centromere) ANAPHASE: chromatids pull apart to opposite ends of the cell TELOPHASE: nuclear membrane reappears, chromatids uncoil into chromatin again
DIVISION OF CYTOPLASM CYTOKINESIS: division of the parent cell’s cytoplasm, occurs right after telophase. In animal cells, a fiber ring forms in the center of the cell, contracts, and pulls cell membrane inward to pinch parent cell into 2 daughter cells. In plant cells, a cell plate grows between the 2 new nuclei. It develops into a membrane & eventually becomes part of the cell wall of the 2 daughter cells. Each DAUGHTER CELL has HALF the cytoplasm of the PARENT CELL. They soon start to grow, eventually becoming the same size as parent cell, and the process continues.