Sanger Sequencing: Principle, Steps, Applications, Diagram 

What is Sanger Sequencing?

Sanger sequencing is a method used to determine the exact sequence of DNA. It is also called the chain termination method because it stops DNA synthesis at specific points.

It is one of the most accurate DNA sequencing techniques used in laboratories.

Sanger Sequencing Principle

The principle of Sanger sequencing is based on:

• DNA replication
• Use of normal nucleotides (dNTPs)
• Use of chain-terminating nucleotides (ddNTPs)

When a ddNTP is added, DNA synthesis stops immediately.

This creates DNA fragments of different lengths, which helps determine the DNA sequence.

 Components of Sanger Sequencing

• DNA template
• Primer
• DNA polymerase
• dNTPs (normal bases)
• ddNTPs (terminating bases)
• Buffer

 Steps of Sanger Sequencing (Step-by-Step)

1. Denaturation

DNA is heated → strands separate

2. Primer Binding

Primer attaches to DNA template

3. DNA Synthesis

DNA polymerase adds nucleotides

4. Chain Termination

ddNTP stops DNA growth

5. Fragment Formation

Different DNA lengths are produced

6. Separation

Fragments separated by electrophoresis

7. Sequence Reading

DNA sequence is identified

 Sanger Sequencing Diagram  

A typical diagram shows:

• DNA template
• Primer
• DNA polymerase
• ddNTP incorporation
• Terminated fragments
• Gel electrophoresis results

This visual helps understand how DNA fragments are analyzed.

 Applications of Sanger Sequencing

• DNA sequencing
• Mutation detection
• Genetic disease diagnosis
• PCR product analysis
• Plasmid verification
• Microbial identification

 Advantages of Sanger Sequencing

• Very high accuracy
• Reliable results
• Easy to interpret
• Ideal for small DNA fragments

 Limitations

• Slow for large DNA
• Expensive per sample
• Low throughput

Why is Sanger Sequencing Still Used?

Even with modern sequencing methods, Sanger sequencing is still used because:

 It is the gold standard for validation
 It provides high-quality results

 Quick Summary 

Sanger sequencing is a DNA sequencing method based on chain termination using ddNTPs, producing DNA fragments of different lengths that are analyzed to determine the DNA sequence.

FAQ 

What is Sanger sequencing used for?

Sanger sequencing is used for DNA sequencing, mutation detection, and genetic analysis.

Why is it called chain termination method?

Because ddNTPs stop DNA synthesis during replication.

Is Sanger sequencing accurate?

Yes, it is one of the most accurate sequencing methods.

What is the read length of Sanger sequencing?

Around 500–1000 base pairs.