Cell Division The Cell Cycle and Cancer
The Phases of the Cell Cycle
Cell Division / Cell Cycle Prokaryotes Chromosomes are simple, circular pieces of DNA Occurs rapidly Cells grow, replicate DNA, then divide in two –Called *Binary Fission Results in two genetically identical cells Eukaryotes Multiple chromosomes, also mixed with proteins and wound tightly –Called *Chromatin (looks like a clump of yarn) # Chromosome varies in organisms Cycle takes more time than prokaryotes, and more complex
Confusing Chromosome Vocabulary Chromosome – bundles of DNA Chromatin – DNA uncondensed, looks like tangled strings Chromatid (sister chromatid) – individual strand of condensed DNA How many chromosomes are in the cell above?
Interphase – “in between” period of growth Majority of a cell’s life is in interphase G1, S, G2 phases G1 = growth of cell S = synthesis (or replicating) of DNA – 2x the DNA G2 = prepare for mitosis (make extra organelles or structures needed for mitosis)
Mitosis = 4 Stages = PMAT Prophase Longest phase of mitosis DNA condenses (becomes visible) Spindles are formed by centrioles Nuclear envelope starts breaking down Centromere – where 2 identical chromatids attach to each other
Metaphase (PMAT) Shortest phase of mitosis Centromeres align the chromosomes across the middle of the cell Spindle fibers attach to centromeres HINT: Metaphase = Middle
Anaphase (PMAT) Sister chromatids pulled apart by spindle fibers Chromosomes (or chromatids) go to opposite ends of the cell Separate chromosomes into two groups HINT: Anaphase = Away/Apart
Telophase (PMAT) Last phase of mitosis (PMAT) Chromosomes spread out into a tangle of chromatin (stringy-looking) Nuclear envelope reforms around both clusters of chromosomes Spindle fibers break down Cell cycle is ALMOST complete
Cytokinesis Cell’s cytoplasm divides to make 2 cells *Animal Cells: cell membrane is flexible and pinches in 2 *Plant Cells: cell wall is not flexible and must create a cell plate, forming 2 plant cells Now have 2 IDENTICAL cells (same DNA - clone)