ESTs,Physical maps,Cytogenic maps

ESTs : ESTs are small pieces of DNA sequence (usually 200 to 500 nucleotides long) that are generated by sequencing either one or both ends of an expressed gene. The 3' ESTs serve as a common source of STSs because of their likelihood of being unique to a particular species and provide the additional feature of pointing directly to an expressed gene.

ESTs as Gene Discovery Resource:As observed ESTs represent a copy of just the interesting part of a genome, that which is expressed, they have proven themselves again and again as powerful tools in the hunt for genes involved in hereditary diseases. ESTs also have a number of practical advantages in that their sequences can be generated rapidly and inexpensively, only one sequencing experiment is needed per each cDNA generated. ESTs are powerful tools in the hunt for known genes because they greatly reduce the time required to locate a gene. Using this method, scientists have already isolated genes involved in Alzheimer's disease, colon cancer, and many other diseases.

Cytogenetic Map:

A cytogenetic map is the visual appearance of a chromosome when stained and examined under a microscope. Particularly important are visually distinct regions, called light and dark bands, which give each of the chromosomes a unique appearance. This feature allows a person's chromosomes to be studied in a clinical test known as a karyotype, which allows scientists to look for chromosomal alterations.

Physical map:

A physical map is a collection of overlapping clones that have been arranged into a tiling path based on either fingerprinting (digestion of clones with restriction enzymes and comparison of the fragment sizes) or hybridisation.

The genetic markers can help to integrate these three maps mentioned above.

For Arabidopsis thaliana, TAIR's comprehensive MapViewer is an integrated graphic display of each Arabidopsis chromosome. TAIR is the internet site where all information and data about Arabidopsis is combined. MapViewer shows genetic, physical, and sequence maps in one site and allows users to search, browse, and align different maps in a region of interest. In the future, all the maps will be fully integrated into a genome map for the organism.