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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?