Allister

Blood cells have no DNA. They're made from certain expressions in our genome being translated into proteins. Once the blood cells are assembled, they do not require DNA to carry out any of their functions.

I think that they may respond to the lighting changes with genetically programmed behaviors. That cats would specifically be able to differentiate the concepts of "night" and "day"; to understand what those abstractions actually mean and apply them, doesn't seem possible to me. Their most developed specialized part of their brain structure is the amygdala. The distinction here is that they wouldn't actually "feel time", because time does not exist to them, but "feel natural lighting", which subtly change behaviors.