Difference between Linker and Adaptor

Linkers and adaptors are oligonucleotides that are useful in DNA ligation. They are chemically synthesised molecules. In recombinant DNA technology, DNA sequences are cut and need ligation to join back the strands. The cleaved DNA often has blunt or sticky ends. Sticky ends are easy to ligate, but DNA strands with blunt ends are hard to ligate. The linker and adaptor molecules then come into play.

The linker and adapter molecules also have internal restriction sites, which help in DNA ligation.

What is a Linker?

The linkers are short double-stranded sequences of DNA. They have blunt ends. They are chemically synthesised oligonucleotides. They are ligated with the blunt ends of a vector of foreign DNA.

It contains restriction sites for the identification of restriction enzymes. The restriction enzymes cleave the ligated linker and the DNA fragment to produce cohesive or sticky ends.

One drawback of linkers is that the foreign DNA fragment sometimes already possesses restriction sites for the enzymes that are used to cut the linker, resulting in cleaving the DNA internally. This limits the use of linker molecules.

Example: Eco-RI linkers and Sal-I linkers

What is an Adaptor?

An adaptor molecule is a double-stranded, chemically synthesised oligonucleotide that is used for the ligation of DNA.

The adaptors have one sticky and one blunt end. The blunt end is ligated with the blunt end of the target DNA producing a DNA fragment with sticky ends. The sticky end helps in the easy ligation of the DNA fragments. The adaptors also have restriction sites that can be used to create new protruding terminuses by the action of restriction enzymes.

One disadvantage of adaptor molecules is that two sticky ends can join to form dimers resulting in the blunt end DNA molecule again. This can, however, be prevented by treating the molecules with alkaline phosphatases.

Uses of adaptor molecules include adding sticky ends to cDNA for easy ligation into the plasmids and similar vector ligations.

Linker Adaptor
Linkers are chemically synthesized oligonucleotides that have two blunt ends. Adaptors are chemically synthesized oligonucleotides with one blunt and one sticky end.
No single-stranded tail is present. A single-stranded tail is present at the sticky end.
The DNA fragment might already have a restriction site, limiting the use of linker molecules. The adaptor molecules tend to join and make dimers.

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Also Read:

Frequently Asked Questions on the Difference between Linker and Adaptor


What are adaptors in PCR?

Adaptors in PCR are used to amplify DNA fragments with arbitrary sequences; it also suppresses non-specific DNA interactions.


What is the difference between primers and adapters?

Primers are short molecules that are required for the initiation of DNA synthesis, whereas adaptors are molecules that are required for ligation purposes.


What are adaptors in DNA sequencing?

Sequence adaptors are short DNA sequences that help in fishing unknown DNA sequences during various techniques.


What are blunt and sticky ends?

Blunt ends are non-cohesive ends where both strands terminate with a base pair. On the other hand, sticky ends are cohesive with non-paired nucleotides on one strand, creating an overhang.


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