As I understand, digital cameras have a unity gain ISO: an ISO setting at which no gain is applied. Below this ISO negative gain is applied, in effect ignoring some of the photons, and above positive gain is applied.
Say for example we have a camera sensor with a 8 bit depth, unity gain ISO at 800, and positive gain is applied analog before the ADC. If an exposure is taken at ISO 1600, will the analog gain result in more quantization levels than if the photo were taken at ISO 800 and then bumped up a stop in post? That is, if the exposure is digitally increased a stop in post, the resulting histogram would be expected to have gaps. A DN of 1 would become 2, 2 to 4, 3 to 6 but there would be no output of 3, 5, etc. but if the gain is applied analog before the ADC, is there the extra data available to fill in those gaps?