Figure 2.

The distribution of observed expression ratios from two, independently-amplified replicates is significantly narrower than that observed from a split cell comparison. A, B – Frequency histograms for averaged log(base2) expression ratios calculated from two dye-swapped replicate hybridizations from whole cortex total RNA (A) and from two dye-swapped split cell (half-vs-half) hybridizations (B). See below for further details of the split cell hybridization procedure. C, D – Plots of intensity versus expression ratios (MA-plots) for averaged microarray data obtained in the two sets of dye-swapped replicate hybridizations shown in A and B. Note that the spread of expression ratios is markedly wider in the split cell comparisons than in the replicate hybridizations.