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Integrated Genome Maps - In the past, genetic maps were prepared by different groups separately, particularly using RFLPs. These 'private maps like private armies induce fights' (E. Robson). Therefore, the data from different sources are now being used and integrated composite maps are being presented.

These maps would have information on linkage distances, chromosome location and physical distances in term of number of base pairs, etc.

During October 1992, two comprehensive maps of the entire human genome became available.

(i) In the first of these maps prepared jointly by hundreds of scientists from National Institute of Health (NIH) and CEPH collaborative group, 1416 loci spread over 90% of the genome were mapped.

This map contains mostly RFLP markers, but also included 279 genes (and expressed sequences) and 339 microsatellites. Only 351 markers (including 205 microsatellites) had heterozygosity of 70% or more (heterozygosity is a measure of variability; maximum heterozygosity for a two allele marker is only 50%).

(ii) Another map, published by about 20 workers at Genethon (a factory for human geneties in France), was based on 792 (C-A) repeat microsatellite markers (600 of them are highly informative). The above two maps may be combined, since both used CEPH families.

A large yeast artificial chromosome (Y AC) contig of human chromosomes was also published in 1992 and it is hoped that the genetic map will soon be integrated with cytogenetic and physical maps (contigs). It is hoped that by the end of 1993, a map with an average marker spacing of less than 1 cM will become available.

Integrated genome maps are also being prepared in other animals particularly mouse and Drosphila. In mouse, a microsatellite based map was published in 1992 and will be integrated with RFLP and RAPD markers earlier mapped.

In Drosophila also integrated molecular maps are being prepared. In 1992, more than 1000 Y AC clones were placed on a physical map through in situ hybridization. In another approach, specific chromosome regions were microdissected and used for preparing overlapping cosmid clones (contig).

An integrated genetic map for Drosophile using linkage data, cytogenetic data and other information has been published in 1992 in a special issue of 'Drosophila Information Service'.

 
 

 

 
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