Nucleic acid sequencing

The determination of the exact base sequence present in a stretch of nucleic acid (particularly in DNA) underpins much of modern molecular biology. Sequencing plays a central role in rDNA cloning experiments, as well as in determining genome data. Two approaches have been developed to sequence DNA: the Maxam-Gilbert chemical sequencing method and the Sanger-Coulson enzymatic sequencing method. Both involve the ultimate generation of a full set of fragments of the DNA strand to be sequenced, as illustrated in Figure 3.11. The methodologies employed ensure that the identity of the final (3') base in each fragment is known. The fragments are then separated on the basis of their size by electrophoresis and, because the identity of the end base in each fragment is already known, the full sequence can simply be read from the ladder of fragments generated. Full details of sequencing methodologies are outside the scope of this book, but they are included in all core molecular biology and biochemistry student textbooks. RNA is sequenced by an enzyme-based method somewhat similar to the enzyme-based DNA method.

DNA strand, with bases numbered

Fragment generation via chemical or enzymatic means

Seperation of each fragment via electrophoresis


Figure 3.11 A simplified overview of the approaches adopted to both chemical and enzyme-based DNA sequencing. Refer to text for details

Supplements For Diabetics

Supplements For Diabetics

All you need is a proper diet of fresh fruits and vegetables and get plenty of exercise and you'll be fine. Ever heard those words from your doctor? If that's all heshe recommends then you're missing out an important ingredient for health that he's not telling you. Fact is that you can adhere to the strictest diet, watch everything you eat and get the exercise of amarathon runner and still come down with diabetic complications. Diet, exercise and standard drug treatments simply aren't enough to help keep your diabetes under control.

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