18 February 2013
Critical Analysis of DNA Replication in Bacteria
DNA replication is a biological process that occurs in all living organisms and copies their DNA; it is the basis for natural inheritance. The process starts when one double-stranded DNA molecule produces two identical copies of the molecule. The cell cycle (mitosis) also pertains to the DNA replication/reproduction process. DNA replication, in eukaryotes, is controlled within the context of the cell cycle. As the cell grows and divides, it goes through stages in the cell cycle; DNA replication occurs during the S phase (synthesis phase). Whereas bacteria do not go through an exact cell cycle but instead, they continuously copy their DNA. The research conducted in this study was to see if, in fact, that cell size had anything to do with the initiation of DNA replication in bacteria. The objectives and hypothesis was clearly stated in the paper. In order to find the answer to their question, the researchers used Escherichia coli (E. coli) and Bacillus subtilis (B. subtilis) in their experiment. Both E. coli and B. subtilis are common and well known bacteria that are used in research. They took the E. coli and B. subtilis and placed them in specific media for each step the in process of replication. They used the process of microscopy to help them see the specimens, since they were unable to see them with their naked eye. They also used flow cytometry to help them to identify and sort through the cells and their DNA by staining them with a fluorescent dye and detecting the fluorescence through a illumination microscope. This helped them to calculate the number of replication forks per cell, along with the cells age and size at initiation. The researcher did an excellent job describing each media and staining technique that they used during their experiments. For example, they explained exactly how much nutrient agar each specimen was placed in during the...
Cited: Demarre G, Chattoraj DK (2010) DNA Adenine Methylation Is Required to Replicate Both Vibrio cholerae Chromosomes Once per Cell Cycle. PLoS Genet 6(5): e1000939. doi:10.1371/journal.pgen.1000939
Hill NS, Kadoya R, Chattoraj DK, Levin PA (2012) Cell Size and the Initiation of DNA Replication in Bacteria. PLoS Genet 8(3): e1002549. doi:10.1371/journal.pgen.1002549
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