Before revision:  Quantitative experiments have revealed two characteristic input-output relations of the system: First, in spatially-graded stimuli, the internal gradients of the signaling molecules at steady state reflect the relative steepness -- rather than the absolute concentration -- of the chemoattractant  along the cell body.
After revision:  Quantitative experiments have revealed two characteristic input-output relations of the system: First, in spatially-graded stimuli, the internal gradients of the signaling molecules are determined by the relative steepness -- rather than the absolute concentration -- of the chemoattractant along the cell body.