146
edits
CH391L/S12/Selectablegeneticmarkers: Difference between revisions
From OpenWetWare
Jump to navigationJump to search
CH391L/S12/Selectablegeneticmarkers (view source)
Revision as of 21:10, 19 February 2012
, 19 February 2012no edit summary
No edit summary |
No edit summary |
||
| Line 4: | Line 4: | ||
[[Image:Antibiotic Resistance Markers.jpg|thumb|right|Example application of selectable genetic markers in nematodes. Only nematodes transfected with markers survive and proliferate<cite>Giordano-Santini2011</cite>.]] | [[Image:Antibiotic Resistance Markers.jpg|thumb|right|Example application of selectable genetic markers in nematodes. Only nematodes transfected with markers survive and proliferate<cite>Giordano-Santini2011</cite>.]] | ||
Selectable genetic markers are exogenous genes that are introduced into a cell, conferring a previously absent resistance. These markers are primarily used to "mark" the successful transformation of DNA into a plasmid. Oftentimes, selectable markers are accompanied by other exogenous genes that is the primary gene of interest; the marker simply serves to distinguish between successful transformations, and unaltered cells | Selectable genetic markers are exogenous genes that are introduced into a cell, conferring a previously absent resistance. These markers are primarily used to "mark" the successful transformation of DNA into a plasmid. Oftentimes, selectable markers are accompanied by other exogenous genes that is the primary gene of interest; the marker simply serves to distinguish between successful transformations, and unaltered cells. | ||
This is where the selectable genetic markers prove their usefulness. For instance, selectable genetic markers can be used to confer ampicillin resistance to E. coli. These newly resistant E. coli can then be grown on culture plates with ampicillin, allowing only E.coli with successfully transformed DNA to proliferate. | It is not atypical to witness transformation efficiencies as low as .05%, making it difficult to pick correct cellular colonies without additional techniques. This is where the selectable genetic markers prove their usefulness. For instance, selectable genetic markers can be used to confer ampicillin resistance to E. coli. These newly resistant E. coli can then be grown on culture plates with ampicillin, allowing only E.coli with successfully transformed DNA to proliferate. | ||
In addition to selectable genetic markers are screenable genetic markers. Screenable genetic markers function in a similar manner in that they are | In addition to selectable genetic markers are screenable genetic markers. Screenable genetic markers function in a similar manner in that they are exogenous genes that are transformed into a cell; however, they do not confer any new sort of resistance to the cell. Instead, they cause the cell to respond differently to environmental conditions in such a way as to distinguish transformed cells from untransformed cells. This can be useful when determining the transformation efficiency of a cell, or when carefully monitoring the activity of proteins. | ||
==Types of Selectable Markers== | ==Types of Selectable Markers== | ||
===Antibiotic=== | ===Antibiotic=== | ||
| Line 14: | Line 14: | ||
===Morphological=== | ===Morphological=== | ||
===Other=== | ===Other=== | ||
[[Image:Alternative Selective Marker.jpg|thumb|left|An alternative technique for selectable markers that avoids antibiotic resistance.]] | [[Image:Alternative Selective Marker.jpg|thumb|left|An alternative technique for selectable markers that avoids antibiotic resistance<cite>Parsons2011</cite>.]] | ||
Recent research into selectable genetic markers has looked into pathways that avoid employing antibiotic and herbicidal resistance. This is due to rising concern over "wild" strains of bacteria or plants developing antibiotic or herbicidal resistance and proliferating rapidly in nature. Even in a laboratory environment, avoiding the resistance approach towards selectable markers can prove beneficial. | |||
A novel approach towards selectable markers was developed in Lawrence Livermore National Laboratory, which employes a toxin/antitoxin combination of genes as a marker. The process, summarized in the figure to the left, effectively avoids the need to grow antibiotic resistant bacterial cultures on an antibiotic plate. An inducible zeta-toxin group is first introduced into an E. coli strain. A DNA strand of interest containing an zeta-antitoxin group is then transformed into the E. coli, and the entire culture is grown. The zeta-toxin is then induced, killing off all E. coli that does not contain the antitoxin group. This <cite>Parsons2011</cite>. | |||
==Types of Screening== | ==Types of Screening== | ||
[[Image:Blue white test.jpg|thumb|right|Successful example of a blue/white screen test. Blue colonies are wild-type cells, while white colonies are successfully transformed cells]] | [[Image:Blue white test.jpg|thumb|right|Successful example of a blue/white screen test. Blue colonies are wild-type cells, while white colonies are successfully transformed cells]] | ||
