Restriction Endonuclease: Difference between revisions
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Restriction endonuclease [[Enzyme|enzymes recognise]] short, specific sequences within [[DNA|DNA]], and then cut the DNA. These enzymes are vital in the process of protein synthesis. The recognition sequence for restriction endonucleases are usually palindromic and symmetrical, this is because the enzymes are made up of 2 identical subunits. The cut leaves a 3’-hydroxyl end, and a 5’-phosphate end on each fragment. | Restriction endonuclease [[Enzyme|enzymes recognise]] short, specific sequences within [[DNA|DNA]], and then cut the DNA. These enzymes are vital in the process of protein synthesis. The recognition sequence for restriction endonucleases are usually palindromic and symmetrical, this is because the enzymes are made up of 2 identical subunits. The cut leaves a 3’-hydroxyl end, and a 5’-phosphate end on each fragment. | ||
These enzymes are found in [[Bacteria|bacteria]], where they defend the cell against [[Bacteriophage|bacteriophages by]] digesting viral DNA. The bacteria protect their own DNA from digestion by modifying it. The method of this modification varies between bacterial species and strains, but the most common method is [[Methylation|methylation]] | These enzymes are found in [[Bacteria|bacteria]], where they defend the cell against [[Bacteriophage|bacteriophages by]] digesting viral DNA. The bacteria protect their own DNA from digestion by modifying it. The method of this modification varies between bacterial species and strains, but the most common method is [[Methylation|methylation]] (different from [[Eukaryotic|eukaryotic methylation]]). | ||
Restriction endonucleases are used in molecular biology to break down DNA into fragments and recombine these fragments in different ways or to insert these fragments into [[Plasmids|plasmids]] for [[Recombinant DNA Technology|recombinant DNA techniques]]. Enzymes such as restriction endonucleases are found in bacteria and archaea and their purpose is to provide a | Restriction endonucleases are used in molecular biology to break down DNA into fragments and recombine these fragments in different ways or to insert these fragments into [[Plasmids|plasmids]] for [[Recombinant DNA Technology|recombinant DNA techniques]]. Enzymes such as restriction endonucleases are found in bacteria and archaea and their purpose is to provide a defence mechanism against foreign molecules such as invading viruses. | ||
Restriction endonucleases are most likely to have | Restriction endonucleases are most likely to have originated from a common ancestor and then, later on, become more widespread due to horizontal gene transformation. | ||
There are two types of restriction enzymes. Endonucleases cut DNA at specific sites within the DNA polymer (middle of strand). There are also [[Exonuclease|Exonucleases]] which cut individual nucleotides from the end of a DNA strand | There are two types of restriction enzymes. Endonucleases cut DNA at specific sites within the DNA polymer (middle of strand). There are also [[Exonuclease|Exonucleases]] which cut individual nucleotides from the end of a DNA strand | ||
The number of restriction fragments generated depends on two factors: | The number of restriction fragments generated depends on two factors: | ||
*The restriction enzyme used (whether it cuts at 4,6 or 8 base pairs) | *The restriction enzyme used (whether it cuts at 4,6 or 8 base pairs) | ||
*The size of the [[Genome|genome]] | *The size of the [[Genome|genome]] (larger genomes produce more fragments) | ||
For example: | For example: | ||
*[[EcoR1|EcoRI]], found in ''[[E. coli|E.coli]]'', recognises the sequence GAATTC, and cuts between the G and the A on both strands | *[[EcoR1|EcoRI]], found in ''[[E. coli|E.coli]]'', recognises the sequence GAATTC, and cuts between the G and the A on both strands<ref>BRADLEY, JR., JOHNSON, DR., POBER BR. (2006) Lecture Notes Medical Genetics. 3rd ed. Maldon, Massachusetts: Blackwell Publishing Inc</ref>. | ||
*[[BamHI|BamHI]] | *[[BamHI|BamHI]] - GGATCC. | ||
*[[Sau3A|Sau3A]] - GATC. | *[[Sau3A|Sau3A]] - GATC. | ||
*[[AluI|AluI]] - AGCT | *[[AluI|AluI]] - AGCT<ref>Dawson,M.T.,Powell,R.,Gannon,F.(1996) Gene Technology. Oxford: BIOS Scientific Publishers Limited.</ref>. | ||
These essential for the genetic engineering enzymes were discovered by [[W.Arber|W.Arber]], [[H.Smith|H.Smith]] and [[D.Nathans|D.Nathans]]. For the discovery of | These essential for the genetic engineering enzymes were discovered by [[W.Arber|W.Arber]], [[H.Smith|H.Smith]] and [[D.Nathans|D.Nathans]]. For the discovery of restriction endonucleases, they were awarded a Nobel Prize in Physiology or Medicine in 1978<ref>Dawson,M.T.,Powell,R.,Gannon,F.(1996) Gene Technology. Oxford: BIOS Scientific Publishers Limited.</ref>. | ||
=== References === | === References === | ||
<references /> | <references /> | ||
Latest revision as of 18:15, 15 October 2018
Restriction endonuclease enzymes recognise short, specific sequences within DNA, and then cut the DNA. These enzymes are vital in the process of protein synthesis. The recognition sequence for restriction endonucleases are usually palindromic and symmetrical, this is because the enzymes are made up of 2 identical subunits. The cut leaves a 3’-hydroxyl end, and a 5’-phosphate end on each fragment.
These enzymes are found in bacteria, where they defend the cell against bacteriophages by digesting viral DNA. The bacteria protect their own DNA from digestion by modifying it. The method of this modification varies between bacterial species and strains, but the most common method is methylation (different from eukaryotic methylation).
Restriction endonucleases are used in molecular biology to break down DNA into fragments and recombine these fragments in different ways or to insert these fragments into plasmids for recombinant DNA techniques. Enzymes such as restriction endonucleases are found in bacteria and archaea and their purpose is to provide a defence mechanism against foreign molecules such as invading viruses.
Restriction endonucleases are most likely to have originated from a common ancestor and then, later on, become more widespread due to horizontal gene transformation.
There are two types of restriction enzymes. Endonucleases cut DNA at specific sites within the DNA polymer (middle of strand). There are also Exonucleases which cut individual nucleotides from the end of a DNA strand
The number of restriction fragments generated depends on two factors:
- The restriction enzyme used (whether it cuts at 4,6 or 8 base pairs)
- The size of the genome (larger genomes produce more fragments)
For example:
- EcoRI, found in E.coli, recognises the sequence GAATTC, and cuts between the G and the A on both strands[1].
- BamHI - GGATCC.
- Sau3A - GATC.
- AluI - AGCT[2].
These essential for the genetic engineering enzymes were discovered by W.Arber, H.Smith and D.Nathans. For the discovery of restriction endonucleases, they were awarded a Nobel Prize in Physiology or Medicine in 1978[3].
References
- ↑ BRADLEY, JR., JOHNSON, DR., POBER BR. (2006) Lecture Notes Medical Genetics. 3rd ed. Maldon, Massachusetts: Blackwell Publishing Inc
- ↑ Dawson,M.T.,Powell,R.,Gannon,F.(1996) Gene Technology. Oxford: BIOS Scientific Publishers Limited.
- ↑ Dawson,M.T.,Powell,R.,Gannon,F.(1996) Gene Technology. Oxford: BIOS Scientific Publishers Limited.