Fission, cell

Morphometric analysis demonstrated that the area of hepatocytes in reference group animals varied within the range of 450 20 pm, and in control groups 460 25 pm. In animals that received ES or IPG, the area of hepatocytes amounted to 650 40 pm in both cases, i.e. authentically increased (p < 0.01) both in regard to reference and control. Total cell quantity in different mitosis phases amounted to 20 3% of total cell quantity in reference rats, 23 4% in control animals, and among rats that received ES or IPG the total amount of fissionable cells increased by 36% on... 

C (O) = Xq cells reproduce by binary fission, cells are indistinguishable, etc. 

Reproduction is by binary fission, meaning a cell divides into two new cells, each of which matures and divides again. Fission takes place every 1,530 mill under ideal conditions. Ideal conditions mean that the growth environment has abundant food, oxygen, and essential nutrients. 

Binary fission During binary fission, a single cell divides transversely to form two new cells called daughter cells. Both daughter cells contain an exact copy of th geneticinformation contained in the parent cell. 

Binary fission- Division of one cell into two cells by the formation of a septum. It is the most common form of cell division in bacteria. 

Yeast Fungus whose thallus consists of single cells that multiply by budding or fission. 

In terms of evolutionary biology, the complex mitotic process of higher animals and plants has evolved through a progression of steps from simple prokaryotic fission sequences. In prokaryotic cells, the two copies of replicated chromosomes become attached to specialized regions of the cell membrane and are separated by the slow intrusion of the membrane between them. In many primitive eukaryotes, the nuclear membrane participates in a similar process and remains intact the spindle microtubules are extranuclear but may indent the nuclear membrane to form parallel channels. In yeasts and diatoms, the nuclear membrane also remains intact, an intranuclear polar spindle forms and attaches at each pole to the nuclear envelope, and a single kinetochore microtubule moves each chromosome to a pole. In the cells of higher animals and plants, the mitotic spindle starts to form outside of the nucleus, the nuclear envelope breaks down, and the spindle microtubules are captured by chromosomes (Kubai, 1975 Heath, 1980 Alberts et al., 1989). 

The majority of bacteria reproduce-by simple binary fission the circular chromosome divides into two identical circles which segregate at opposite ends ofthe cell. At the same time, the cell wall is laid down in the middle ofthe cell, which finally grows to produce two new cells each with its own wall and nucleus. Each ofthe two new cells will be an exact copy of the original cell from which they arose and no new genetic material is received and none lost. 

For many years, it was thought that binary fission was the only method of reproduction in bacteria, but it is now known that there are three methods of reproduction in which genetic exchange can occur between pairs of cells, and thus a form of sexual reproduction is exhibited. These processes are transformation, conjugation and transduction. Further details ofthese processes as they affect antibiotic resistance will be found in Chapter 9. 

If a single cell reproduces by binary fission, then the number of bacteria n in any generation will be as follows ... 

In phase B it is assumed that the inoculum has adapted itself to the new environment and growth then proceeds, each cell dividing into two. Cell division by binary fission may take place every 15-20 minutes and the increase in numbers is exponential or logarithmic, hence the name log phase. Phase C, the stationary phase, is thought to occur as a result of the exhaustion of essential nutrients and possibly the accumulation... 

Chlamydias, however, are bacteria and have been shown to possess a cell wall containing muramic acid (section 2.2.1), to contain ribosomes of the bacterial (prokaryotic) type, to reproduce themselves by binary fission and to be inhibited by antibiotics active against bacteria. 

This group of microorganisms shares with chlamydias the property of growing only in living tissue. Rickettsiae occur as small (0.3 x 0.25/mi) rod-shaped or coccoid cells. They can be stained by special procedures. Division is by binary fission. They may be cultivated in the blood of laboratory animals or in the yolk sac of the embryo of the domestic fowl, and it is by this method that the organism is grown to produce vaccines. 

In contrast, cells of Pseudomonas acidovorans strain M3GY during growth with biphenyl have been shown to degrade DDE with the fission of one ring and production of 4-chlorobenzoate (Hay and Eocht 1998). 

Booher, R., and Beach, D. (1986). Site-specific mutagenesis of cdc2+, a cell cycle control gene of the fission yeast Schizosaccaromyces pombe. Mol. Cell. Biol. 6 3523-3530. Booher, R. N., Alfa, C. E., Hyams, J. S., and Beach, D. H. (1989). The fission yeast cdc2/cdcl3/sucl protein kinase regulation of catalytic activity and nuclear localization. CeU 58 485-497. 

Bueno, A., and Russell, P. (1993). Two fission yeast B-type cyclins, cig2 and cdc 13, have different functions in mitosis. Mol. Cell. Biol. 13 2286-2297. 

---