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Genes are often grouped into families based upon regions of protein homology and, frequently the nucleotide sequences of the protein coding regions have sufficient nucleotide homology to cross hybridize. In addition, 3 untranslated regions sometimes contain Alu sequences and other repeat elements which can cross hybridize. For these reasons, the 3 insert-specific primer was designed to amplify a portion of the cDNA including little or no coding region and excluding repeat elements. Hence, this design increases hybridization specificity when using the discovery-3 microarray by minimizing the chances that the DNA in any given spot will cross hybridize with RNA-derived probes from other gene family members or with repeat elements.
Each GeneConnection discovery-3 microarray has
control spots distributed throughout the microarray in a defined pattern to
assist in quality control and orientation of the microarray. There are five
types of control spots: spotting buffer only, human -actin DNA, and three Arabidopsis thaliana DNA. The A. thaliana genes
were selected because they are involved in plant-specific processes and do not
have known human homologues. In addition, they do not hybridize to
membrane-arrayed human cDNA from 29 different tissues. In gene expression
profiling experiments, the human -actin gene should
hybridize with most, if not all, human R
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