Chain termination method

Definition

The chain termination method, also known as Sanger sequencing, is a technique for DNA sequencing based on the selective incorporation of chain-terminating dideoxynucleotides during DNA replication. It was developed by Frederick Sanger in 1977 and remains a fundamental method for characterizing DNA sequences.

5 Must Know Facts For Your Next Test

1. The chain termination method utilizes dideoxynucleotides (ddNTPs) which lack a 3’ hydroxyl group, preventing further elongation of the DNA strand.
2. The process involves four separate reactions, each containing one of the four ddNTPs (ddATP, ddTTP, ddCTP, or ddGTP).
3. Sequencing results are read using gel electrophoresis or capillary electrophoresis to separate DNA fragments by size.
4. Fluorescently labeled ddNTPs allow for automated sequencing and detection through laser-induced fluorescence.
5. Though newer technologies like next-generation sequencing have emerged, Sanger sequencing is still widely used for smaller-scale projects and verification of results.

Review Questions

• What role do dideoxynucleotides play in the chain termination method?
• How are the products of Sanger sequencing typically analyzed?
• Why might researchers still use Sanger sequencing despite the availability of next-generation sequencing technologies?

Related terms

Dideoxynucleotide (ddNTP): A modified nucleotide lacking a 3' hydroxyl group that terminates DNA strand elongation.

Gel Electrophoresis: A technique used to separate nucleic acids or proteins based on their size and charge.

Next-Generation Sequencing (NGS): Advanced high-throughput methods capable of rapidly sequencing large amounts of DNA.