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analysis. It enables detection and localization of mismatched or unmatched
nucleotides within heteroduplex DNA. EMD employs natural enzymes from cel-
lular DNA recombination and repair systems that have been successfully selected
and adapted for use in vitro. These enzymes recognize structural differences in
DNA that arise from biochemical comparisons between normal and mutant DNA
samples. This structural comparison can identify mutations much more effectively
than the laborious process of direct determination of the entire DNA sequence of
the gene. The entire procedure takes about 2 h and all the steps can be automated.
Detection sensitivity approaches 98 %. Optimized microchip electrophoresis
devices, combined with EMD methods, have been used to determination SNP sites
in the p53 suppressor gene.
DNA Microarrays
Most genetic disorders are caused by point mutations. Deletions are less frequent
and may be overlooked by DNA mapping. It is diffi cult to fi nd the location of a gene
buried in the tangle of chromosomal DNA in the nucleus; sequencing of individual
nucleotide bases may be required. DNA sequence analysis is a multistep process
comprising sample preparation, generation of labeled fragments by sequencing
reactions, electrophoretic separation of fragments, data acquisition, assembly into a
fi nished sequence, and most importantly, functional interpretation. Sequencing is
also used to determine protein sequences, but it is diffi cult to determine protein
function from sequence. Sequencing is now automated. Sequencing technologies
are described in a special report on this topic (Jain 2015b ). Apart from their impact
on hereditary neurologic diseases, high-throughput genome sequencing technolo-
gies will improve our understanding of sporadic neurologic diseases as well, par-
ticularly those with low-penetrant mutations in the gene for hereditary diseases or
de novo mutations (Tsuji 2013 ).
Role of Sequencing in Personalized Medicine
Among various technologies, sequencing will play an important role in the develop-
ment of personalized medicine as shown in Fig. 2.1.
Whole Genome Sequencing and Personalized Medicine
The role of sequencing in personalized medicine is supported by the latest effort in
personal genome sequencing, Quake’s genome sequence in 2010, which was
undertaken as an integrated analysis of a complete human genome in a clinical
2 Molecular Diagnostics in Personalized Medicine