Restriction enzyme: Difference between revisions
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Restriction [[Endonucleases|Endonucleases]] recognise and cut [[DNA|DNA]] at a specific palindromic base sequences, normally 4, 6 or 8 bases long, and are used selectively to cut DNA into defined fragments at sites known as '[[Restriction site|restriction sites]]'. Different restriction endonucleases are obtained and purified from different species of [[Bacteria|bacteria]]. These [[Enzymes|enzymes]] are made in [[Bacteria|bacteria]] to degrade viral DNA. Cutting [[DNA]] with restriction enzymes can produce fragments with either [[Blunt ends|blunt]] or [[‘sticky’ ends|sticky ends]]. Different restriction enzymes recognise different DNA sequences. The product of a restriction enzyme can have either [[Sticky ends|sticky ends]] or [[Blunt ends|blunt ends]] as shown below. <br> | Restriction [[Endonucleases|Endonucleases]] recognise and cut [[DNA|DNA]] at a specific palindromic base sequences, normally 4, 6 or 8 bases long, and are used selectively to cut [[DNA|DNA]] into defined fragments at sites known as '[[Restriction site|restriction sites]]'. Different restriction endonucleases are obtained and purified from different species of [[Bacteria|bacteria]]. These [[Enzymes|enzymes]] are made in [[Bacteria|bacteria]] to degrade viral DNA. Cutting [[DNA]] with restriction enzymes can produce fragments with either [[Blunt ends|blunt]] or [[‘sticky’ ends|sticky ends]]. Different restriction enzymes recognise different DNA sequences. The product of a restriction enzyme can have either [[Sticky ends|sticky ends]] or [[Blunt ends|blunt ends]] as shown below. <br> | ||
Examples of restriction endonucleases are: | Examples of restriction endonucleases are: | ||
*[[EcoRI|''Eco''RI]]- recognises the sequence 5'GAATTC'3 - [[Sticky ends|sticky ends]] | *[[EcoRI|''Eco''RI]] - recognises the sequence 5'GAATTC'3 - [[Sticky ends|sticky ends]] | ||
*[[BamHI|''Bam''HI]]- recognises the sequence 5'GGATCC'3 - [[Sticky ends|sticky ends]] <br> | *[[BamHI|''Bam''HI]] - recognises the sequence 5'GGATCC'3 - [[Sticky ends|sticky ends]] <br> | ||
* | *[[HhaI|''HhaI'']] - recognises the sequence 5'GCGC'3 - [[Sticky ends|sticky ends]] | ||
* | *''[[XhoI|XhoI]]'' - recognises the sequence 5'CTCGAG'3 - [[Sticky ends|sticky ends]] | ||
*'' | *''[[HindIII|HindIII]]'' - recognises the sequence 5'AAGCTT'3 - [[Sticky ends|sticky ends]] | ||
*'' | *''[[PstI|PstI]]'' - recognises the sequence 5'CTGCAG'3 - [[Sticky ends|sticky ends]] | ||
* | *''[[Sau3A|Sau3A]]'' - recognises the sequence 5'GATC'3 (produces the same [[‘sticky’ ends|sticky ends]] as [[BamHI|BamHI]] upon cutting) | ||
*[[HaeIII|HaeIII]] - recognises the sequence 5'GGCC'3 - [[Blunt ends|blunt ends]] <br> | *[[HaeIII|HaeIII]] - recognises the sequence 5'GGCC'3 - [[Blunt ends|blunt ends]] <br> | ||
Entire genomes can be digested into defined fragments by Restriction enzymes, this is called a [[Restriction Digest|Restriction Digest]]. The number of fragments formed in a digest is dependent on 2 factors: | Entire genomes can be digested into defined fragments by Restriction enzymes, this is called a [[Restriction Digest|Restriction Digest]]. The number of fragments formed in a digest is dependent on 2 factors: | ||
#The restriction enzyme used; A 4bp recogniser will statistically cut a | #The restriction enzyme used; A 4bp recogniser will statistically cut a [[Genome]] in to more fragments than a 6 or 8 bp recogniser because it is more likely for there to be a repeated sequence of less bp. | ||
#The size of the genome; Smaller genomes (10-100 bp, found in viruses) give fewer fragments than larger genomes (>10<sup>6</sup>, found in e.g. humans). <sup></sup><br> | #The size of the genome; Smaller genomes (10-100 bp, found in viruses) give fewer fragments than larger genomes (>10<sup>6</sup>, found in e.g. humans). <sup></sup><br> | ||
Also see [[Restriction endonucleases|Restriction endonucleases]] | Also see [[Restriction endonucleases|Restriction endonucleases]]<ref>Alberts B, Johnson A, Lewis J, Raff M, Roberts K and Walter P. (2008) Molecular Biology of the Cell, Fifth Edition, New York, Garland Science.</ref><br> | ||
=== References<br> === | === References<br> === | ||
<references /> | <references /> | ||
Latest revision as of 09:44, 30 October 2018
Restriction Endonucleases recognise and cut DNA at a specific palindromic base sequences, normally 4, 6 or 8 bases long, and are used selectively to cut DNA into defined fragments at sites known as 'restriction sites'. Different restriction endonucleases are obtained and purified from different species of bacteria. These enzymes are made in bacteria to degrade viral DNA. Cutting DNA with restriction enzymes can produce fragments with either blunt or sticky ends. Different restriction enzymes recognise different DNA sequences. The product of a restriction enzyme can have either sticky ends or blunt ends as shown below.
Examples of restriction endonucleases are:
- EcoRI - recognises the sequence 5'GAATTC'3 - sticky ends
- BamHI - recognises the sequence 5'GGATCC'3 - sticky ends
- HhaI - recognises the sequence 5'GCGC'3 - sticky ends
- XhoI - recognises the sequence 5'CTCGAG'3 - sticky ends
- HindIII - recognises the sequence 5'AAGCTT'3 - sticky ends
- PstI - recognises the sequence 5'CTGCAG'3 - sticky ends
- Sau3A - recognises the sequence 5'GATC'3 (produces the same sticky ends as BamHI upon cutting)
- HaeIII - recognises the sequence 5'GGCC'3 - blunt ends
Entire genomes can be digested into defined fragments by Restriction enzymes, this is called a Restriction Digest. The number of fragments formed in a digest is dependent on 2 factors:
- The restriction enzyme used; A 4bp recogniser will statistically cut a Genome in to more fragments than a 6 or 8 bp recogniser because it is more likely for there to be a repeated sequence of less bp.
- The size of the genome; Smaller genomes (10-100 bp, found in viruses) give fewer fragments than larger genomes (>106, found in e.g. humans).
Also see Restriction endonucleases[1]
References
- ↑ Alberts B, Johnson A, Lewis J, Raff M, Roberts K and Walter P. (2008) Molecular Biology of the Cell, Fifth Edition, New York, Garland Science.