Difference Between Linker and Adaptor

The key difference between linker and adaptor is that a linker does not have cohesive ends while an adaptor has one cohesive end.

DNA ligation is the process of joining two DNA molecules together, forming phosphodiester bonds. The enzyme called DNA ligase catalyzes this reaction. It is one of the critical steps in modern molecular biological fields such as recombinant DNA technology and DNA cloning. The ligation efficiency depends on the ends of DNA molecules to be ligated. There are two types of DNA ends as sticky ends and blunt ends. Ligation efficiency is high with sticky ends than with blunt ends. If the target DNA molecules have blunt ends, molecules called adaptors or linkers will be useful. Adaptors and linkers are chemically synthesized oligonucleotide molecules that help in DNA ligation. They have internal restriction sites as well. Adaptor has one sticky end and one blunt end, while linker has two blunt ends.

CONTENTS

1. Overview and Key Difference
2. What is a Linker 
3. What is an Adaptor
4. Similarities Between Linker and Adaptor
5. Side by Side Comparison – Linker vs Adaptor in Tabular Form
6. Summary

What is a Linker?

Linker is a chemically synthesized oligonucleotide sequence that is double-stranded. Linker has two blunt ends. Linker is used to ligate DNA molecules that have blunt ends to vectors. It contains one or more internal restriction sites. These restriction sites work as recognition sites for restriction enzymes.

After ligation, DNA is restricted again with restriction enzymes to produce cohesive ends. EcoRI-linkers and sal-I linkers are commonly used linkers.

What is an Adaptor?

An Adaptor is a double-stranded oligonucleotide sequence used to link two DNA molecules together. It is a short sequence with one blunt end and one sticky or cohesive end. Therefore, it consists of a single-stranded tail at one end, which enhances the efficiency of DNA ligation.

Moreover, the adaptor has internal restriction sites. Therefore, after ligation, DNA can be restricted with appropriate restriction enzymes in order to create a new protruding terminus. One disadvantage of adaptors is that two adaptors can form dimmers by base pairing with themselves. This can be avoided by treating them with the enzyme called alkaline phosphatase.

What are the Similarities Between Linker and Adaptor?

• Both linker and adaptor are double-stranded short oligonucleotide sequences.
• They carry internal restriction sites.
• Moreover, they are chemically synthesized DNA molecules and are synthetic molecules.
• They can link two DNA molecules together.
• After ligation of linkers and adaptors, the DNA is again restricted with restriction enzymes in order to produce sticky ends.

What is the Difference Between Linker and Adaptor?

A linker is a chemically synthesized short oligonucleotide duplex with two blunt ends. An adaptor is a chemically synthesized short oligonucleotide duplex with one sticky end and one blunt end. Thus, this is the key difference between linker and adaptor. Moreover, adaptors can form dimers, while linkers do not form dimers. So, this is another significant difference between linker and adaptor.

Below is a summary of the differences between linker and adaptor in tabular form.

Summary – Linker vs Adaptor

Linker and adaptor are two types of chemically synthesized oligonucleotides that are useful in ligating blunt-end DNA. Linker has two blunt ends, while adaptor has one blunt end and one cohesive end. So, this is the key difference between linker and adaptor. They are double-stranded molecules that have internal restriction sites.  They are widely used in recombinant DNA technology and DNA cloning.

Reference:

1. “Linker DNA.” Wikipedia, Wikimedia Foundation, 31 Aug. 2020, Available here.
2. Rothstein, R.J., et al. “[7] Synthetic Adaptors for Cloning DNA.” Methods in Enzymology, Academic Press, 7 Jan. 2004, Available here.

Image Courtesy:

1. “BLESS workflow (update v2)” By Karahavet – Own work (CC BY-SA 4.0) via Commons Wikimedia
2. “Library preparation for the SOLiD platform” By Philippe Hupé – Emmanuel Barillot, Laurence Calzone, Philippe Hupé, Jean-Philippe Vert, Andrei Zinovyev, Computational Systems Biology of Cancer Chapman & Hall/CRC Mathematical & Computational Biology, 2012 (CC BY-SA 3.0) via Commons Wikimedia