the genome study mapped DNA not RNA?

Answer 1

The genome itself is made of DNA. But before you have the whole sequence people often start to sequence those sequences that are really expressed (and not "junk") and needed by a cell. mRNA is the expressed gene-"form", converted its the cDNA. Those sequences of an organism, that are derived from actively expressed genes only are called ESTs, expressed sequence tags. ESTs are already spliced and ready to use for further analyses. There are databases derived from ESTs, the genome and also cDNA librarys.

Answer 2

For a better answer Google "definition DNA"
and "definition RNA"
Also Google "genome study"
http://www.genomestudy.com/