Chain termination method

The chain termination or Sanger or dideoxy method is a process used to sequence (read the bases of) DNA. It is named after Frederick Sanger who developed the process in 1975. Variations on the classical Sanger method have led to the development of an automated sequencing method.

Related Topics:
Sequence - DNA - Frederick Sanger - 1975

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In the chain termination method, the DNA segment to be sequenced is replicated over and over. Dideoxynucleotides are added to randomly stop the creation of DNA at each of the four bases (depending on the substance), producing pieces of DNA of almost every length. The lengths of the DNA strands can be worked out using gel electrophoresis. Markers on each strand show which base each strand ends with. When the results from the strands are combined, it is possible to work out the sequence of bases at any point.

Related Topics:
Dideoxynucleotides - Gel electrophoresis

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Because only one base pair can be read off for each strand produced during the process, only a small section of DNA can be reliably sequenced this way. Therefore longer segments of DNA are sequenced using methods (such as chromosome walking and shotgun sequencing) which sequence multiple short strands in such a way that they can be "assembled" to reveal the sequence of a much longer strand.

Related Topics:
Chromosome walking - Shotgun sequencing

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