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+<blockquote>
+<p><strong>Sample Processing:</strong> Samples were processed in the INIA Bioanalytical Core at the W. Harry Feinstone Center for Genomic Research, The University of Memphis, led by Thomas R. Sutter. All processing steps were performed by Shirlean Goodwin. In brief, RNA purity was evaluated using the 260/280 nm absorbance ratio, and values had to be greater than 1.8. The majority of samples were 1.9 to 2.1. RNA integrity was assessed using the Agilent Bioanalyzer 2100. We required an RNA integrity number (RIN) of greater than 8. This RIN value is based on the intensity ratio and amplitude of 18S and 28S rRNA signals. The standard Eberwine T7 polymerase method was used to catalyze the synthesis of cDNA template from polyA-tailed RNA using Superscript II reverse transcriptase (Invitrogen Inc.). The Enzo Life Sciences, Inc., BioArray High Yield RNA Transcript Labeling Kit (T7, Part No. 42655) was used to synthesize labeled cRNA. The cRNA was evaluated using both the 260/280 ratio (values of 2.0 or 2.1 are acceptable) and the Bioanalyzer output (a dark cRNA smear on the 2100 output centered roughly between 600 and 2000 nucleotides is required). Those samples that passed both QC steps (10% usually failed and new RNA samples had to be acquired and processed) were then sheared using a fragmentation buffer included in the Affymetrix GeneChip Sample Cleanup Module (Part No. 900371). Fragmented cRNA samples were either stored at -80 deg. C until use or were immediately injected onto the array. The arrays were hybridized and washed following standard Affymetrix protocols.</p>
+
+<p><strong>Replication and Sample Balance:</strong> We obtained a male sample pool and female sample pool from each isogenic group. While all strains were orginally represented by matched male and female samples, not all data sets passed the final quality control steps. Seventy-seven of 97 strains are represented by pairs or (rarely) trios of arrays. The first and last samples are technical replicates of a B6D2F1 hippocampal pool (aliquots R1291H3 and R1291H4).</p>
+
+<p><strong>Experimental Design and Batch Structure:</strong> This data set consists arrays processed in six groups over a three month period (May 2005 to August 2005). Each group consists of 32 to 34 arrays. Sex, strain, and strain type (BXD, CXB, and MDP) were interleaved among groups to ensure reasonable balance and to minimize group-by-strain statistical confounds in group normalization. The two independent samples from a single strain were always run in different groups. All arrays were processed using a single protocol by a single operator, Shirlean Goodwin.</p>
+
+<p>All samples in a group were labeled on one day, except for a few cases that failed QC on their first pass. The hybridization station accommodates up to 20 samples, and for this reason each group was split into a large first set of 20 samples and a second set of 12 to 14 samples. Samples were washed in groups of four and then held in at 4 deg C until all 20 (or 12-14) arrays were ready to scan. The last four samples out of the wash stations were scanned directly. Samples were scanned in sets of four.</p>
+</blockquote>