The HsaI restriction enzyme from the embryos of human, Homo sapiens, has been isolated with both the tissue extract and nuclear extract. It proves to be an unusual enzyme, clearly related functionally to Type II endonuclease.

A restriction site is a sequence of approximately 6–8 base pairs of DNA that binds to a given restriction enzyme. These restriction enzymes, of which there are many, have been isolated from bacteria. Their natural function is to inactivate invading viruses by cleaving the viral DNA.

The option Find Restriction Sites… from the “Tools”→“Cloning” menu or the context menu allows you to find and annotate restriction sites on a nucleotide sequence.

There exist an enzyme, called restriction enzyme, that can identify a particular nucleotide sequence, called restriction sites, and perform cleaving operation. This process separates genetic material into smaller fragments which may contain gene(s) of interest.

Restriction enzyme, also called restriction endonuclease, a protein produced by bacteria that cleaves DNA at specific sites along the molecule. In the bacterial cell, restriction enzymes cleave foreign DNA, thus eliminating infecting organisms.

Restriction enzymes are used in biotechnology to cut DNA into smaller strands in order to study fragment length differences among individuals. This is referred to as restriction fragment length polymorphism (RFLP). They’re also used for gene cloning. Knowledge of these unique areas is the basis for DNA fingerprinting.

These enzymes contain more than one subunit and require AdoMet and ATP cofactors for their roles in DNA methylation and restriction digestion, respectively. They are components of prokaryotic DNA restriction-modification mechanisms that protect the organism against invading foreign DNA.

Restriction endonucleases are enzymes that cut double-stranded DNA at very specific recognition sites. They were originally discovered in bacteria that use them to restrict the growth of viruses but are now among the workhorse enzymes of biotechnology and recombinant DNA research.

Answer: Type II enzymes, which are predominantly used in biotechnology, cut DNA within the recognized sequence without the need for ATP and are smaller and simpler. Type II restriction enzymes are named according to the bacterial species from which they are isolated.

Today, scientists recognize three categories of restriction enzymes: type I, which recognize specific DNA sequences but make their cut at seemingly random sites that can be as far as 1,000 base pairs away from the recognition site; type II, which recognize and cut directly within the recognition site; and type III.

Type II enzymes are simpler and don’t require ATP as an energy source, unlike Type I. Type III cleaves the DNA at approximately 25 base pairs from the recognition sequence and, like Type I, requires ATP. Endonucleases contribute to DNA repair.

SmaI is an example of a restriction enzyme that cuts straight through the DNA strands, creating DNA fragments with a flat or blunt end. Other restriction enzymes, like EcoRI, cut through the DNA strands at nucleotides that are not exactly opposite each other.

When selecting restriction enzymes, you want to choose enzymes that:

1. Flank your insert, but do not cut within your insert.
2. Are in the desired location in your recipient plasmid (usually in the Multiple Cloning Site (MCS)), but do not cut elsewhere on the plasmid.

Type II restriction endonucleases (REases) are sequence-specific endonucleases that recognize short DNA sequences and cut the DNA at defined positions within or close to the recognition sequence. In the producer cell, the host DNA is protected by specific methylation of the recognition sequence.

The orthodox type II restriction endonuclease is a homodimer of ∼2 × 30 kDa molecular mass, which recognizes a palindromic sequence 4–8 bp in length, and in the presence of Mg2+ cleaves the two strands of the DNA within or immediately adjacent to the recognition site to give a 5′-phosphate and a 3′-OH end.

Restriction enzymes (originally isolated from bacteria) cut double-stranded DNA at particular nucleotide sequences into fragments, usually four, five, or six nucleotides long. A restriction enzyme will cleave the DNA wherever the particular recognition sequence (or restriction site) of the enzyme occurs.

Key points: Restriction enzymes are DNA-cutting enzymes. Each enzyme recognizes one or a few target sequences and cuts DNA at or near those sequences. Many restriction enzymes make staggered cuts, producing ends with single-stranded DNA overhangs.

BamHI (from Bacillus amyloliquefaciens) is a type II restriction endonuclease, having the capacity for recognizing short sequences (6 bp) of DNA and specifically cleaving them at a target site. This allows the DNA to maintain its normal B-DNA conformation without distorting to facilitate enzyme binding.

The number of cuts in an organism’s DNA made by a particular restriction enzyme is determined by the number of restriction sites specific to that enzyme in that organism’s DNA.

A restriction enzyme is an enzyme isolated from bacteria that cuts DNA molecules at specific sequences. The isolation of these enzymes was critical to the development of recombinant DNA (rDNA) technology and genetic engineering.

3,000 restriction enzymes

Introduction. Restriction enzyme digestion takes advantage of naturally occurring enzymes that cleave DNA at specific sequences. There are hundreds of different restriction enzymes, allowing scientists to target a wide variety of recognition sequences. For a list of many commonly used restriction enzymes, visit NEB.

A restriction digest is a procedure used in molecular biology to prepare DNA for analysis or other processing. These enzymes are called restriction endonucleases or restriction enzymes, and they are able to cleave DNA molecules at the positions at which particular short sequences of bases are present.

EcoRI creates 4 nucleotide sticky ends with 5′ end overhangs of AATT. Other restriction enzymes, depending on their cut sites, can also leave 3′ overhangs or blunt ends with no overhangs.

Time-Saver qualified enzymes can cut substrate DNA in 5-15 minutes and safely digest overnight. For enzymes that are not Time-Saver Qualified, the recommended incubation time is 1 hr. In general, long incubations (several hours to overnight) are not recommended, unless digesting some gDNAs.

To open the Destroy Restriction Site dialog, click Actions → Restriction Cloning → Destroy Restriction Site…, or simply press the Delete key.

Incomplete digestion may occur when too much or too little enzyme is used. The presence of contaminants in the DNA sample can inhibit the enzymes, also resulting in incomplete digestion.

Storage. Storage at -20°C is recommended for most restriction enzymes. For a few enzymes, storage at -70°C is recommended for periods longer than 30 days.