This is how the Marker on the Sprawl was made. In Dead Space 2 it is revealed that both Markers revealed codes that give information on how to create more Markers.In Dead Space: Martyr, Hennessy becomes increasingly insane the closer he comes to the Black Marker, after he kills his co-pilot, Dantec, the Symbols flash in his head and he is overwhelmed with the urge to write them down, and he uses the only thing he has, the blood of Dantec, once the entire sub is covered he has used all of Dantec's blood, and all of the wall space so he is forced to use his own blood and body to finish the Symbols, he dies shortly after.Most of the symbols that are written all over the walls in the Ishimura seem to mostly be written in blood, though some are written in marker pen.Marker Symbols are commonly mislabeled 'Unitology Symbols' because of their strong association and use with Unitology.The symbols represented DNA which was why the Marker was a double helix with these symbols on it representing the DNA of the Necromorphs. He even mentioned this in the Dementia Trailer. As Isaac's dementia set in, he began to hear the symbols whispering to him. Included among the graffiti scattered throughout the USG Ishimura and the Sprawl, Marker Script is readily apparent. Marker Symbols are a set of symbols produced by the Markers.

Dead space marker symbol