As others have pointed out it is possible to deduce where genes are by looking at the sequence however this is by no means straightforward DNA is spaghetti code of the very worst kind.
It is possible to "run the DNA to see what it produces", basically when a (DNA) gene is active copy's of its sequence are made in messenger RNA (mRNA, its like DNA but much less stable) the mRNA copy's are perhaps akin to compiled code as there is a fair amount of rearrangement that goes on before its '3D printed' in protein.
Now its possible to take the mash up cells or tissue extract the mRNA convert it back to DNA (stabilising it) then sequence the different DNA molecules to find out what genes are active in a given tissue.
Mapping the sequences back to the genes is not straight forward, genes can exist in multiple identical or near identical copy's making it hard to map back, some genes never express or only express under very specific circumstances or only in certain people