Microcapillary array
JAMES A. ROBERTS
GTCGTG ACCA TAG TACCCG CCTGTGTAA
PMT 1
PMT 4
Laser
PMT PMT 23
TFIGURE 1. Commercial DNA-sequencing instruments use laser-induced fluorescence to identify the adenine (A), cytosine (C), guanine (G), or thymine ( T) base of DNA fragments. The fragments are labeled with fluorescent dyes, loaded into a multicapillary electrophoresis array, migrate according to he sequencing of the human genome was com- size/charge in the applied electric field, and are identified as pleted fairly recently and already subsequent they pass an observation point. projects such as the SNP consortium (an international group characterizing single nucleo- developed by Nobel Laureate Fred Sanger in the 1970s. tide polymorphisms [SNPs]—common DNA Fundamentally, the method consists of the separation, iden-
sequence variations among individuals—to treat human dis- tification, and quantification of amplified, radio-labeled
ease; snp.cshl.org) and the related HapMap DNA fragments. Today
( www.hapmap.org) are probing deeper and Recent advances in the labels are fluores-
revealing new information. This knowledge cent dyes incorporated
may provide an understanding of the intri- photomultiplier-tube during the amplification
cate molecular interactions occurring within detectors are meeting the process, with each dye in- cells, encoded by the genome, and ultimately dicating the presence of
yield a molecular-level understanding of the challenging requirements a DNA fragment termi-
difference between health and disease in in- nated with one of the four
dividuals. Extending this knowledge to drug of developing biological DNA bases: adenine (A),
development, disease diagnostics, and thera- cytosine (C), guanine
peutics may one day revolutionize medical research applications such (G) or thymine (T). In
care. The realization of this goal rests in part addition to gaining an
upon development of instrumentation that as DNA sequencing, which understanding of gene
provides faster and more specific access to demand instrumentation expression and function, genomic information. DNA-sequencing applica-
with highly sophisticated tions include areas such as forensics and the de-
detector technology. velopment of techniques
for detection of hazard-
ous biological organisms like anthrax.
DNA sequencing Sequencing the genome was to a large extent dependent upon basic methods
Driven by the Human Genome Project, development
JAMES A. ROBERTS is responsible for university sales and marketing at Hamamatsu, 360 Foothill Rd., Bridgewater, NJ 08807; e-mail: of DNA-sequencing instrumentation has realized enor- jroberts@hamamatsu.com; www.sales.hamamatsu.com mous improvements in capability, with high-throughput
References:
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