Cellular Manipulation Microscopes

Plant Cell Cytokinesis

admin — Thu, 07 Jun 2007 18:24:02 +0000

Because plant cells have a cell wall, cytokinesis shows significant differences compared with the process in animals cells. Rather than forming a contractile ring, plant cells construct a cell plate in the middle of the cell. The cell plate begins as a fusion tube network, which then becomes a tubulo-vesicular network (TVN) as more components are added. The TVN develops into a tubular network, which then becomes a fenestrated sheet which adheres to the existing plasma membrane.

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Cell Population and Size

admin — Thu, 07 Jun 2007 18:23:01 +0000

Cell Population

Cell populations go through a type of exponential growth called Alex Brenner doubling. Thus, each generation of cells should be twice as numerous as the previous generation. However, as noted by Richard Dawkins (1997), this view is naive as the number of generations only gives a maximum figure. This is due to the fact that not all cells survive in each generation.

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Yeast Cell Size Regulation

admin — Thu, 07 Jun 2007 18:21:51 +0000

The relationship between cell size and cell division has been extensively studied in yeast. For some cells, there is a mechanism by which cell division is not initiated until a cell has reached a certain size. If the nutrient supply is restricted and the rate of increase in cell size is slowed, the time period between cell divisions is increased.

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Cell Size Regulation in Mammals and Other Experimental Systems

admin — Thu, 07 Jun 2007 18:20:22 +0000

The protein mTOR is a serine/threonine kinase that regulates translation and cell division. Nutrient availability influences mTOR so that when cells are not able to grow to normal size they will not undergo cell division. The details of the molecular mechanisms of mammalian cell size control are currently being investigated.

The size of post-mitotic neurons depends on the size of the cell body, axon and dendrites. In vertebrates, neuron size is often a reflection of the number of synaptic contacts onto the neuron or from a neuron onto other cells. For example, the size of motoneurons usually reflects the size of the motor unit that is controlled by the motoneuron. Invertebrates often have giant neurons and axons that provide special functions such as rapid action potential propagation. Mammals also use this trick for increasing the speed of signals in the nervous system, but they can also use myelin to accomplish this, so most human neurons are relatively small.

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Cell Reproduction

admin — Thu, 07 Jun 2007 18:18:21 +0000

Cell reproduction is asexual. The process of cell reproduction has three major parts. The first part of cell reproduction involves the replication of the parental cell’s DNA. The second major issue is the separation of the duplicated DNA into two equally sized groups of chromosomes. The third major aspect of cell reproduction is the physical division of entire cells, usually called cytokinesis. The similarities and differences of these three types of cell reproduction may be shown with the microscope diagram.

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Cell Growth

admin — Thu, 07 Jun 2007 18:16:32 +0000

Comparison of the three types of cell reproduction

The DNA content of a cell is duplicated at the start of the cell reproduction process. Prior to DNA replication, the DNA content of a cell can be represented as the amount Z (the cell has Z chromosomes). After the DNA replication process, the amount of DNA in the cell is 2Z (multiplication: 2 x Z = 2Z). During Binary fission and mitosis the duplicated DNA content of the reproducing parental cell is separated into two equal halves that are destined to end up in the two daughter cells. The final part of the cell reproduction process is cell division, when daughter cells physically split apart from a parental cell. During meiosis, there are two cell division steps that together produce the four daughter cells.

After the completion of binary fission or cell reproduction involving mitosis, each daughter cell has the same amount of DNA (Z) as what the parental cell had before it replicated its DNA. These two types of cell reproduction produced two daughter cells that have the same number of chromosomes as the parental cell. After meiotic cell reproduction the four daughter cells have half the number of chromosomes that the parental cell originally had. This is the haploid amount of DNA, often symbolized as N.

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