Submit Article |Resources | Link to us | Sitemap | Search | Language
Back to Home
Home >> Gene Concept >>Electron Microscope Heteroduplex Mapping
Back to Home

Electron Microscope Heteroduplex Mapping -

The existence of genetically well defined deletion mutations at the r- II locus has permitted E.K.F

Bautz and colleagues to determine the physical size of the r- II locus.

This was done using a technique called heteroduplex mapping.

A heteroduplex is a DNA molecule in which the strands are not entirely complementary.

Heteroduplex mapping involves the in vitro preparation of DNA hetero duplexes and their analysis by electron microscopy.

The wild type T4 phage DNA is isolated after growing in E. coli cells with radiolabelled PO4 The mutant phage was also grown on E. coli cells without radiolabelled PO4.

Then DNA is isolated from both the wild and mutant phages and is denatured by heating to 100°C. The denatured DNAs are then mixed together and then allowed to renature by incubating the mixture at 60°C for 12 hours. Some heteroduplexes will be forming with one strand of DNA from the wild type T4 and one strand from the mutant phage.

The wild type strand of these heteroduplexes will not have complementary base sequences with which to pair in the segment of the mutant type DNA molecule

The wild type strands will thus form single-stranded loops, the length of which can be measured on electron micrographs.

Bautz and co-workers prepared heteroduplexes between DNA from T 4 r+ phage and DNA from each of several genetically well-characterized r- II deletion mutants; they then analysed them by electron microscopy.

Their results yielded estimates of 1800 , 70 bp for r-IIA and 845 i: 50 bp for r-IIB lotus. These results combined with the extensive genetic data of Benzer and colleagues, provide a fairly clear picture of the fine structure of the r- II locus.
 

 
Submit Article |Resources | Link to us | Sitemap | Search | Language
English|Français|Español|Deutsch|Italiano|Portugues|Japanese|Korean|Sim-Chinese| Language