Maxam-Gilbert method

   In 1976-1977, Allan Maxam and Walter Gilbert developed a DNA sequencing method which is also called the chemical Cleavage method because it is based on chemical modification of DNA and subsequent cleavage at specific bases.

Procedure

   The DNA to be sequenced must be denatured first so that the two strands can be separated from each other, one strand is purified and divided into four samples and is tagged as G, A+G, A+T, and C. Each of which sample is treated with one of the modifying chemical reagents and cleavage reagents. The former cause a chemical modification in the nucleotides they are specific for, making them to susceptible to cleavage while the later are used to cut DNA strand at a specific point. In the sample "G" the unknown DNA fragment will be cleaved from all those points where G is present. Similarly, in sample "A+G" the fragment will be cleaved from A as well as G and so on in other samples. After the completion of the reaction, the products are run through gel electrophoresis and finally, the sequence is read from the autoradiograph of gel pattern.