DNA SEQUENCING - RECENT INNOVATIONS AND FUTURE-TRENDS

Determination of the sequence of DNA is one of the most important aspe cts of modem molecular biology. New sequencing methods currently being developed enable DNA sequence to be determined increasingly faster an d more efficiently. One of the major advances in sequencing technology is the development of automated DNA sequencers. These utilize fluores cent rather than radioactive labels. A laser beam excites the fluoresc ent dyes, the emitted fluorescence is collected by detectors, and the information analyzed by computer. Robotic work stations are being deve loped to perform template preparation and purification, and the sequen cing reactions themselves. Research is currently in progress to develo p the technology of mass spectrometry for DNA sequencing. Success in t his endeavor would mean that the gel electrophoresis step in DNA seque ncing could be eliminated. A major innovation has been the application of polymerase chain reaction (PCR) technology to DNA sequence determi nation, which has led to the development of linear amplification seque ncing (cycle sequencing). This very powerful yet technically simple me thod of sequencing has many advantages over conventional techniques, a nd may be used in manual or automated methods. Other recent innovation s proposed recently to increase speed and efficiency include multiplex sequencing. This consists of pooling a number of samples and processi ng them as pools. After electrophoresis, the DNA is transferred to a m embrane, and sequence images of the individual samples are obtained by sequential hybridizations with specific labeled oligonucleotides. Mul tiplex DNA sequencing has been used in conjunction with direct blottin g electrophoresis to facilitate transfer of the DNA to a membrane. Che miluminescent detection can also be used in conjunction with multiplex DNA sequencing to visualize the image on the membrane.