BiologyICSE Articles Biology

Restriction Enzymes


“Resistance enzymes are enzymes produced by certain bacteria that have the property of cleaving DNA at or near specific base sequences.”

restriction enzymes types

What are Restriction Enzymes?

A restriction enzyme is a protein produced by bacteria that cleaves DNA at specific sites. This position is known as the limiting position.

Antimicrobial enzymes protect healthy bacteria from predators. They recognize the bacteriophage at restriction sites, cleave, and destroy its DNA.

Restriction enzymes are important tools for genetic engineering. They can be isolated from bacteria and used in the laboratory.

Inhibitory enzymes recognize short, specific nucleotide sequences in DNA known as recognition sequences. When a restriction enzyme recognizes a DNA sequence, it analyzes the interactions between adjacent nucleotides and cuts the DNA.

Bacteria prevent degradation of their DNA sequence by adding methyl groups to adenine or cytosine bases within the recognition sequence with the help of the enzyme methylase.

Types of Restriction Enzymes

  • These restriction enzymes cut DNA from recognition sequences. However, they do not form complex inhibitory blocks, so they have little practical value.
  • These are complex enzymes, with multiple catalytic and modifying domains. They were originally thought to be rare, but genomic analysis has shown them to be common and of great biological interest.
  • These enzymes cleave at specific sites near or at restricted sites. Discrete restriction blocks and gel band patterns were observed. Laboratories use it extensively for DNA analysis and gene cloning.
  • They are a family of unrelated proteins. They are named after the bacterial species from which they were isolated. For example, EcoRI is isolated from the bacterial strain E.coli.
  • Restriction enzymes make two different types of cuts. When DNA is cut in the middle of the recognition sequence, bad ends are formed, and the sticky ends form extensions.
  • They are multifunctional proteins consisting of two domains: Res and Mod. This is a revolutionary methyltransferase. The specific DNA sequence of this sequence is recognized by the Mod region.


They are used in RFLP techniques that cut DNA into small fragments to study fragment length differences between individuals.

During cloning, the gene is inserted into a plasmid. Restriction enzymes cut the plasmid to form a long single-stranded structure. Two DNA molecules are joined with the help of DNA ligase to form a single DNA molecule.

Related Articles

Leave a Reply

Your email address will not be published. Required fields are marked *

Back to top button