Guanine + cytosine content

Like all bacteria, actinomycetes are prokaryotic microorganisms. In addition, the adenine-thymine and guanine-cytosine contents of bacteria and actinomycetes are similar, as are the cell wall constituents of both types of microorganisms. Actinomycetes filaments are also about the same size as those of bacteria. 

Table 6.10. The guanine +cytosine content of cestode DNAs compared with other groups (Data from Normore, 1976 Barrett, 1981)...

Hurst LD, Merchant AR. High guanine-cytosine content is not an adaptation to high temperature a comparative analysis amongst prokaryotes. Proc. Biol. Sci. 2001 268 493 97. 

Sueoka N., Marmur J., Doty P. (1959). Heterogeneity in deoxyribonucleic acids II. Dependence of the density of deoxyribonucleic acids on guanine-cytosine content. Nature 183 1429-1433. 

Furthermore, the results helped to characterize how nucleic acid molecules are adsorbed on clay minerals including kaolinite [28, 29], For example, double stranded DNA molecules that differ in their guanine-cytosine content were adsorbed in equal amounts by clays including kaolinite [49]. Linear DNA was revealed to be adsorbed on illite and kaoUnite to a greater extent than on montmorillonite [60]. This emphasizes the influence that positive charges of the lattice edges and the microorganization of clay particles have on the mechanism of DNA adsorption. 

Tobia, A., C. L. Schildkraut, and J. J. Maio. 1970. DNA replication in synchronized cultured mammalian cells. I. Time of synthesis of molecules of different average guanine + cytosine content. J. Molec. Biol., 54 499-515. 

Early in the S period, DNA has an average GC (guanine-cytosine) content of 43.6%, while in the late S period the GC content is 38.7%. This transition of synthesis from a relatively rich early GC DNA to a relatively rich late AT (adenine-thymine) DNA appears to be a general property of mammalian cells (Tobia et al., 1970), but its signficiance is unknown. 

Since the RNA molecule is a single strand complementary to only one of the two strands of a gene, its guanine content does not necessarily equal its cytosine content, nor does its adenine content necessarily equal its uracil content. 

A complete understanding of the biochemical functions of DNA requires a clear picture of its structural and physical characteristics. DNA has significant absorption in the UV range because of the presence of the aromatic bases adenine, guanine, cytosine, and thymine. This provides a useful probe into DNA structure because structural changes such as helix unwinding affect the extent of absorption. In addition, absorption measurements are used as an indication of DNA purity. The major absorption band for purified DNA peaks at about 260 nm. Protein material, the primary contaminant in DNA, has a peak absorption at 280 nm. The ratio A26(j/A2m is often used as a relative measure of the nucleic acid/protein content of a DNA sample. The typical A260/Am for isolated DNA is about 1.8. A smaller ratio indicates increased contamination by protein. 

The guanine and cytosine content (expressed as the percentage of total base groups) of these three types of DNA are 39, 50 and 66%, respectively. 

Mandel, M., and Marmur, J. (1968). Use of ultraviolet absorbance-temperature profiles for determining the guanine plus cytosine content of DNA. Methods Enzymol 12B 195. 

The causes of these differences lie on the physicochemical reactivity properties inherent to each probe sequence. For example, a broadly used parameter in molecular genetics for its essential role in primer affinity is the guanine-cytosine percentage (i.e., GC content) of the oligonucleotide. Another cause, in this case associated to the probe-mapping locus, is the distance to the 3 -end of the gene. This was primarily reported by the 3 -IVT designs of Ajfymetrix microarrays. The 3 -poly-A amplification performed before the hybridization in these devices can considerably bias the abundance measures detected,... 

Kagawa Y., Nojima H., Nukima N., Ishizuka M., Nakajima T., Yasuhara T., Tanaka T., Oshima T. (1984). High guanine plus cytosine content in the third letter codons of an extreme thermophile. J. Biol. Chem. 259 2956-2960. 

Muto A. and Osawa S. (1987). The guanine and cytosine content of genomic DNA and bacterial evolution. Proc. Natl. Acad. Sci. USA 84 166-169. 

Naya H., Romero H., Zavala A., Alvarez B., Musto H. (2002). Aerobiosis increases the genomic guanine plus cytosine content (GC%) in prokaryotes. J. Mol. Evol. 55 260-264... 

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