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Cellular Reproduction Chapter 8 Why must cells reproduce? • “All cells come from previously existing cells.” (Virchow, 1858) • Continuity of life (binary fission in prokaryotes, mitosis and/or meiosis in eukaryotes) from generation to generation. • Growth and development in multicellular organisms. (each of us grew from a single cell) • Repair of damaged tissues. (healing of wounds) “Like begets like” • Only applies to asexual reproduction (binary fission, mitosis)…these processes produce two daughter cells which are genetically identical. • In sexual reproduction, offspring resemble, but are not genetically identical to, parents. Prokaryotes Reproduce Using Binary Fission The Cell Cycle Governs the Life of Eukaryotic Cells Stages of the Cell Cycle Interphase: (90%) • G1: Increase in cell size, prepares to copy DNA • S: DNA replication occurs • G2: More growth, preparation for mitotic phase Mitotic Phase: (10%) • Includes nuclear (mitosis) and cytoplasmic (cytokinesis) divisions In eukaryotic cells, DNA is packaged as chromosomes at start of G1 Chromosomes are made of chromatin, a combination of DNA and support after S phase proteins…resembles a thread that is wrapped around multiple spools. Duplicated chromosomes are at end of mitotic phase referred to as “sister chromatids” During much of the cell cycle (interphase), chromosomes are not condensed or visible. Why? How does the process of Mitosis produce genetically identical daughter cells?