Mutation, in DNA

Describe a biosensing protocol for detecting mutations in DNA samples. 

DNA CT also permits chemistry at a distance. Oxidative DNA damage and thymine dimer repair can proceed in a DNA-mediated reaction initiated from a remote site. These reactions too are sensitive to intervening DNA dynamical structure, and such structures can serve to modulate DNA CT chemistry. The sensitivity of DNA CT to base pair stacking also provides the basis for the design of new DNA diagnostics, tools to detect mutations in DNA and to probe protein-DNA interactions. 

Together these data suggest that bile acids may induce mutations in DNA, and reinforces the notion that bile acids may play a key role as carcinogens or co-carcinogens in the gastro-intestinal tract. 

Mutations in DNA polymerase or thymidine kinase may result in resistance. Acyclovir-resistant HSV strains that exhibit thymidine kinase deficiency are also resistant to famciclovir and penciciovir. 

The deamination of 5-methylcytosine occurs more frequently than that of other bases but the product, thymine, is of course a normal base and therefore will not be recognized by the repair system (Fig. 6.42). This represents a major source of point mutations in DNA. 

Southern blotting is a technique that can detect mutations in DNA. It... 

G. Wang, and W. Knoll, Detection of Point Mutations and Insertion Mutations in DNA Using a Quartz Crystal Microbalance and MutS, a Mismatch Binding Protein, Anal. Clwm. 2004, 76. 489. 

M. J. Heller, Rapid Determination of Single Base Mismatch Mutations in DNA Hybrids by Direct Electric Field Control , Proc. Natl. Acad Sci. USA, 94(4), 1119-1123(1997). 

These rare tautomer forms A, T, C and G are of concern since it has been suggested that these may serve as a source for point mutations in DNA since the pyrimidine tautomer of one WC pair is now complementary to the purene of the other WC pair and vice versa. The genetic implication of these tautomer forms can be appreciated by considering the following scheme. 

Sosnowski RG, Tu E, Butler WF, O Connell JP, Heller MJ. Rapid determination of single base mismatch mutations in DNA hybrids by direct electric field control. Proc Natl Acad Sci USA 1997 94(4) 1119-1123. 

This sensor size may thus be better suited for biological assays where a yes-or-no answer is required or only a small degree of signal quantification is needed. A potential application is the detection of mutations in DNA that occur in one or few nucleotides only, the so called SNPs (Single Nucleotide Polymorphisms). In this case it is then necessary to distinguish accurately between almost identical DNA strands and it only matters if the particular mutation being probed is present or not. 

Figure 6-5. Rapid and sensitive methods for detecting mutations in DNA. (a) Denaturing gradient gel electrophoresis. (b) Single-strand conformation polymorphism.

Kuypers AWHM, Willems PMW, van der Schans MJ, Linssen PCM, Wessels HMC, de Bruijn CHMM, Everaerts FM, Mensink EJBM (1993) Detection of point mutations in DNA using capillary electrophoresis in a polymer network. J Chromatogr 621 149-156. 

It can further be argued that comparing two persons with different oxidative stress to DNA, i.e. different urinary excretion rates, the one with the higher stress will statistically have a higher chance for a mutation in DNA. Increased levels can not necessarily be interpreted in the same way, unless it can be established whether it originates from increased stress or decreased repair. 

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