Cell Reproduction, Chapter 11, 2007

Cell Reproduction, Chapter 11, 2007 - The Continuity of...

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Click to edit Master subtitle style The Continuity of Life: Cell Reproduction
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Roles of Cell Division In unicellular organisms what is the result of cell division?
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Prokaryotic cells divide by a simple process known as binary fission: www.emc.maricopa.edu www.brooklyn.cuny.edu This is a form of asexual reproduction and produces two offspring that are identical (except for inherited mistakes– mutations ).
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Binary fission in eukaryotes Unicellular eukaryotes– mostly protists– also reproduce by binary fission. However , binary fission in eukaryotes is much more complicated. Why? Eukaryotic cells, unlike those of prokaryotes, have pairs of linear chromosomes (each with two free ends). Producing two identical eukaryotic cells from one parent cell involves a process known as mitotic cell division , requiring cytoskeletal elements to facilitate the separation of chromosomes into two identical groups. In any case, in binary fission in general, the genetic material of each of the two new cells will be identical to that of the parent cell.
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Roles of cell division in multicellular organisms Compensation for cell growth, maintaining a cell size that allows efficient exchange of materials with the environment Replacement of unhealthy and dying cells Allowing for the organism’s growth– think hippopotamus or redwood, versus mouse or a tiny herbaceous plant (all of which have cells whose size, on average, is similar in different species) REMINDER: Production of a new multicellular organism from a zygote (a fertilized ovum) involves making many cells from one. Growth and development: A sand dollar embryo, shortly after its first cell division Tissue renewal: Dividing bone marrow cells will produce new blood cells.
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The Cell Cycle Although most cells reproduce , they typically devote only a small part of their lives to this process. During part of their life, cells increase in mass; that is, they grow . They also replicate their DNA . Without this process the two new cells formed during reproduction would not be genetically identical. The proportion of a cell’s life spent in each of the above three phases varies considerably from species to species.
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Prokaryotic cell cycle, revisited: The entire cell cycle in prokaryotes– involving growth, DNA replication, and binary fission– typically takes only about 20-30 minutes. From one prokaryotic cell, reproducing under ideal conditions, over a million new individuals can result in as little as 7 or 8 hours! Don’t forget– Each time such a cell completes cell division and forms two new cells, both can go through the cycle again.
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This note was uploaded on 04/09/2008 for the course BIOLOGY 101 taught by Professor Beitch during the Fall '07 term at Quinnipiac.

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Cell Reproduction, Chapter 11, 2007 - The Continuity of...

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