BCM6223 Restriction Enzymes

Restriction enzymes

Bacteria uses these enzymes to defend themselves against bacteriophages; they restrict invasion by cutting the phosphodiester backbone, resulting in double-stranded breaks.

endonuclease R (later changed to EcoB)

This is the enzyme responsible for endonucleolytic scission.

EcoK

Second restriction enzyme in E. coli discovered.

Haemophilus influenzae

The discovery of the first successful RE was from the isolation and characterization of this bacteria.

HindII

This is the first ever RE discovered; it is site-specific deoxyribonuclease that cleaves DNA palindromic sequence AAGCTT in the presence of Mg2+ via hydrolysis.

False. REs are rare in eukaryotes.

Restriction enzymes are also found in eukaryotes.

T or F?

Genus of the bacteria from which the enzyme originates

[RE NOMENCLATURE]

Where is the first letter of 3-letter abbreviation from?

species of the prokaryotic cell from which they were isolated

[RE NOMENCLATURE]

Where are the second 2 letters from?

True.

[RE NOMENCLATURE]

Strain designation is sometimes included.

T or F?

Numbers

[RE NOMENCLATURE]

_______ following the nuclease names indicate the order in which the enzymes were isolated from single strains of bacteria.

Type I REs

This type of RE cuts DNA at random sequences far from their recognition sequences.

Type II REs

This type of RE cuts DNA at defined positions close to or within their recognition sequences.

Type III REs

This type of RE cleaves DNA within their recognition sequences.

Type I and III REs

These 2 restriction enzyme types bind to the DNA at their recognition sequences but cut DNA at some distance away.

Type II REs

This RE type cleaves the DNA within their recognition sequences for specific manipulation of DNA.

palindromes

DNA sequences recognized by type II REs are short inverted repeats termed _________, of 4-8 bp.

Sticky ends

These ends are short, single-stranded overhangs resulted from staggered cuts.

Has both 3'- and 5'-protruding ends because they tend to bond with complementary sequences of bases.

Blunt ends

These ends result from the cutting of both strands of DNA directly opposite each other.

Endonuclease

This term applies to sequence specific nucleases that break nucleic acid chains somewhere in the interior of the molecule.

exonuclease

Nucleases that function by removing nucleotides from the ends of the molecule are called?

6-base sequences

Most of the REs recognize __-base sequences.

Rare cutters

These REs cut less frequently like NotI.

Isoschizomers

These REs have the same recognition sequences but have different cutting sites.

modification enzymes

Cells protect its own DNA from inadvertent destruction by its own REs by what enzymes?

methylating

Modification consists of ____ specific bases within the recognition sequence.

Methylases

These are enzyems that perform modification.enzymes

5'-end

Each resulting fragment of sticky ends has a protruding __'-end composed of unpaired bases.

ligase

This enzyme is then used to join the phosphate backbones of the 2 molecules.

True.

The cellular origin, or even the species origin, of the sticky ends does not affect their stickiness.

T or F?

Once the cuts have been made, the resulting fragments are held together only by the relatively weak ______ bonds

Hydrogen

The weakness of these hydrogen bonds allows the DNA fragments to ______ from eachother

separate