Base composition, of DNA

Binding of berberine caused changes in the circular dichroic spectrum of all B-DNAs with an increase of molar ellipticity of the 270 nm band the molar ellipticity value at saturation depended strongly on the base composition of DNA being larger for the AT-rich DNA than the GC-rich DNA. However, the generation of berberine-associated extrinsic circular dichro-ism bands was not dependent on the base composition or sequence of base pairs. 

The base composition of DNA generally varies from one species to another. 

The base composition of DNA in a given species does not change with an organism s age, nutritional state, or changing environment. 

Base Composition of DNAs Made from Single-Stranded Templates Predict the base composition of the total DNA synthesized by DNA polymerase on templates provided by an equimolar mixture of the two complementary strands of bacteriophage 0X174 DNA (a circular DNA molecule). The base composition of one strand is A, 24.7% G, 24.1% C, 18.5% and T, 32.7%. What assumption is necessary to answer this problem ... 

Base Composition of DNAs from Different Sources... 

Describe a physical method that can be used to estimate the base composition of DNA. Describe the data obtained with two DNA samples One with high G-C content and another with high A-T content (Assume that the concentration of the samples is equal.)... 

In an early work on the compositions of DNA, Chargaff (1955) noted that the ratios of adenine to thymine and of guanine to cytosine are very close to unity in a very large number of DNA samples. This observation has been used to support the helical structure of DNA proposed by Watson and Crick (1953). From the base compositions of DNA and RNA given in the following tables, deduce the statistical significance for the statement that the base ratios (A/T(U) and G/C are unity for DNA but vary for RNA (Note Calculate the ratios first and then perform statistical analysis on the ratios). 

Estimate Tm of the sample by plotting the melting curve. Perform regression analysis to deduce the correlation between Tm and the base composition of DNA by comparing the following data of DNAs from other sources ... 

The base composition of DNA from many different species has been determined. It varies from one to another (see Table 7.1). 

Question What is the base composition of DNA from human kidney ... 

It is the same as for human liver, as shown in Table 7.1, because the base composition of DNA is a characteristic of a particular species and does not vary from one cell type to another. This reflects the fact that the nucleotide sequence, and therefore the genetic information present, in each type of cell within an organism is exactly the same. However, as will be seen later, this information is expressed differently in the various cell types of an organism (Chap. 17). 

Firstly, the determination of the base composition of DNA from a number of sources had shown that while the overall base composition varied widely, there was always the same amount of A as of T, and the same amount of G as of C. Secondly, high-quality X-ray photographs of DNA fibres were consistent with a helical structure composed of either two or three polynucleotide chains. The major physiological form of the DNA double helix is the B-DNA described by the X-ray pictures of Rosalind Franklin, with 10 base parrs per turn (Figure 3.18),... 

The interaction between DNA and proflavine was studied by means of the heating of mixing. From the results, the thermodynamic quantities were estimated for the DNA-proflavlne system by an intercalation process. The thermodynamic results show that the intercalation process of DNA-proflavlne system would be expected to be dominated by the enthalpy rather than the entropy. In addition, the heat of interaction depends on GC base composition of DNA the heat of interaction between GC base pairs and proflavine is greater than that between AT base pairs and proflavine. 

In this paper, we attempt to elucidate the thermodynamic quantities of the interaction in the dye binding by intercalation process and also explore the effect of GC base composition of DNA on dye binding by measuring the heat of mixing of proflavine (PF) and Cl. perfrlngens DNA (DNA I), E. coll DNA (DNA II) and M, lysodelktlcus DNA (DNA III), respectively because the interaction for Intercalation process is based on the interaction between dye and base pairs of DNA. 

As seen In Table II, the values of AH for each system are different and decrease with decreasing GC base composition of DNA although the values of AG are nearly equal. The AH dependence on GC base composition of DNA seems to be based on difference of the heat of Interaction between GC base pairs and PF and between AT base pairs and PF. 

Gutteridge, W. E., Trigg, P. I., and Williamson, D. H. (1969). Base compositions of DNA from some malarial parasites. Nature 224,1210-1211. 

The X-ray diffraction pattern of DNA demonstrated the helical structure and the diameter. The combination of evidence from X-ray diffraction and chemical analysis led to the conclusion that the base pairing is complementary, meaning that adenine pairs with thymine and that guanine pairs with cytosine. Because complementary base pairing occurs along the entire double helix, the two chains are also referred to as complementary strands. By 1953, studies of the base composition of DNA from many species had already shown that, to within experimental... 

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