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Home >> Plant Biotechnology and Genomics >>Construction of Molecular Maps and Synteny (Collinearity) >>Molecular Genetics Maps (High Density)

Molecular Genetics Maps (High Density)
Although molecular genetic maps are now available in majority of crops, most of these maps are inadequate for identification of candidate genes and for subsequent map based cloning of genes. Therefore, efforts have been underway to prepare high-resolution maps in several crops. One of the approaches followed in maize in this connection involved intermating among plants in F2 and subsequent generations to provide for an opportunity for increased recombination. When such a population after five-generations of intermating was used in maize, it led to the production of a high resolution map, in which the map distance increased from 1532 cM to 5917 cM.

Intermated RILs were also used in maize to prepare a high density SSR map involving 978 SSRs. In sorghum also, high density map with - 3000 marker loci spread over 3000 cM was later produced during 2000-2002. A high-density genetic linkage map of tetraploid cotton was also developed, which had 2662 loci (RFLPs involving 75% cDNA and 25% gDNA RFLPs; 5% SSRs), which were distributed in 26 linkage groups and spanned a genetic distance of over 4700 cM. An integrated high density map in Aegilops tauschii genome, which represents the D genome of bread wheat, was also published in 2002; this map had 732 loci. In several crops including bread wheat and maize, efforts have also been make to identify gene-rich genomic regions (these regions are also shown to be the recombination hot-sports) in the maps. These gene rich regions are being subjected not only to high resolution mapping but also to genome-wide sequencing.

 

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