Physical mapping

A physical map of a chromosome or a genome that shows the physical locations of genes and other DNA sequences of interest. Physical maps are used to help scientists identify and isolate genes by positional cloning.
According to the ICSM (Intergovernmental Committee on Surveying and Mapping), there are five different types of maps: General Reference, Topographical, Thematic, Navigation Charts and Cadastral Maps and Plans.

1. Physical mapping Dr. Priya Trivedi M.Sc.(BOTANY), M.Ed., Ph.D . (BOTANY)

2. A physical map gives the actual distances in number of bases between genes on a chromosome. As such, it describes the structural characteristics of the chromosome itself. The physical map is one in which chromosomes are cut into large fragments, then copied (or cloned) many millions of times. The copies are then analyzed with a goal of finding segments that overlap. Rearranging these overlapping segments reconstitutes the chromosome. Distance is expressed in Megabase pairs ( need not be proportionate to recombination frequencies).

3. Restriction Mapping

4. Fluorescence in situ Hybridization (FISH)

5. Sequence tag sites or STSs

6. Chromosome walking

7. Principle Identification of fragments with overlapping sequences may be a key to the reconstruction or characterization of large chromosome regions. Using the conventional cloning techniques to isolate fragments, one may be able to isolate >100kb chromosome region per month. In addition, pulsed field gel electrophoesis may be used to isolated >100 kb DNA fragments, which may be cloned.

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