Wischusen- Bio exam 4 - Cell Cycle The Life of a Cell...

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° Cell Cycle: The Life of a Cell Starts with cytokinesis G1 phase (G=gap) S phase: DNA replication/synthesis G2 Phase o G1-G2 = interphase Mitosis: cell division ° Chromosome Structure Eukaryote chromosomes composed of DNA and histone proteins o During interphase: DNA is relaxed, extended o During cell division: DNA is supercoiled, condensed Chromosomes can be unreplicated : 1 molecule of DNA Chromosomes can be replicated : 2 identical molecules of DNA, held together G1 starts and ends with unreplicated chromosomes, goes into S At the end of S phase, DNA is doubled (replicated) but still same number of chromosomes o Amount of DNA changes, but not the amount of chromosomes Stays that way through G2 Start cell division with same amount of chromosomes Cell Reproduction Two Steps: Division of the nucleus: karyokinesis (two forms = mitosis, meiosis) Division of the cytoplasm: cytokinesis *do not necessarily have to have to occur together; two separate processes that occur with separate mechanisms* ° Mitosis Produces identical daughter cells (nuclei) o Identical to each other o Identical to parental cell ° ° ° ° ° ° ° ° ° ° Steps of Mitosis: 1. Prophase : nuclear envelope breaks down, spindle apparatus forms, chromosomes condense and attach to the spindle 2. Metaphase : chromosomes have moved to the center of the cell and have lined up on the metaphase plate 3. Anaphase : replicated chromosomes separate, leaving them unreplicated 4. Telophase : chromosomes have moved to poles of spindle, bunched into two groups ° Cytokinesis Division of the cytoplasm -4 replicated chromosomes -8 DNA -4 replicated chromosomes -8 DNA -8 unreplicated chromosomes -8 DNA -8 unreplicated chromosomes -8 DNA 1) Prophase 2) Metaphase 3) Anaphase 4) Telophase 1
Roughly cut into equal parts (generally) In animal cells: Cleavage o Microfilaments contract and the cell cuts itself in two In plant cells: Cell Plate Formation o Vesicles form a cell plate in the inside of cell ° How do the Chromosomes move on the spindle?

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