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Bio1A03 Biology Complex Multicellular Appropriate Organism McMaster University

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McMaster University

Bio1A03 Biology Complex Multicellular Appropriate Organism McMaster University

Theme 4:DNA Replication and MitosisModule1:The Cell Cycle
“Cell proliferation(division) in prokaryotes”
The ability for a pre-existing cell to give rise to another cell is due to the regulatedprocess of cell division.This process of cell division can mean different things to
different organisms.
For some cells, such as prokaryotic cells, cell division is also reproduction since thedivision of one prokaryotic cell will give rise to a new organism (made up of one cell).
All of the essential elements necessary to reproduce cells are found in the prokaryoticcell.
These cells are capable of making exact copies of their genomes and then segregating onecopy of each genome to each of two daughter cells.
The process of cell division in prokaryotes requires that identical genetic material isdistributed amongst daughter cells.
In prokaryotes, the process of cell division is a form ofasexual reproductionthat isoften referred to asbinary fission.
The process of cell division in prokaryotes isinitiatedwhen the DNA of the bacterialchromosome is attached by proteins to the inside of the plasma membrane.
DNA replication can then begin along an origin of replication region of the bacterialchromosome.
As the chromosome continues to replicate, the cell begins to elongate, and the newlysynthesized DNA is also anchored to the plasma membrane.
As binary fission progresses, the cell continues to elongate until the two DNA attachmentsites are atopposite endsof the elongated cell.
When DNA replication is complete and the bacterium is approximately doubleits original                                                Early embryos containstem cellswhich are unspecialized cells that can both reproduce indefinitelyand under appropriate conditions, are able to differentiateinto specialized cells of one or more types.
After an organism is fully grown, cell division can then lead to continual renewal and repair of cells that make up various tissues.                                                                                                                                                                                            The adult body also has stem cells, but in contrast to embryonic stem cells, these adult stem cells are not able to give rise to all cell types in the organism, but instead are able to replace non-reproducingspecialized cells.
For example:
-the mammalian adult skeletal muscle is a stable tissue that has very little cell turnover,or cell division.
-when muscle cells undergo injury, quiescent (or non-dividing) satellite stem cells that are present in the basement membrane of the muscle tissueare able to become                                                                                                                          “activated” and once again begin dividing to enable muscle regeneration.
-The activation of these satellite stem cells leads to theproliferation,differentiation andfusionof muscle precursor cells called myoblasts
-become committed to forming themature muscle cellsthat make up muscle fibers (or myofibers)Once these myofibers are formed, they are no longer able to divide.


Bio1A03 Biology Complex Multicellular Appropriate Organism McMaster University

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