The Affymetrix GeneChip® product range
for gene expression analysis enables researchers to qualitatively and quantitatively
study the gene expression levels in several model organisms (see table 1 and
Affymetrix for a complete list of catalog arrays). Alternatively
the Custom Express ™ Array Program and NimbleExpress™ Array Program can be used to design
GeneChip® expression arrays representing 520 to 61,000 sequences
per array and study any completely sequenced genome or user-specific subset
of genes.
High-quality RNA is an absolute prerequisite to obtain
reliable and reproducible data. Based on our experiences with a variety
of organisms ranging from yeast over mammalian tissues to Drosophila and
Arabidopsis we provide you with advice on how to isolate RNA from your samples.
For the standard protocol 1 µg of total RNA is needed, but, if tissue
or cells are limited, a small sample protocol can be used that reduces
this starting amount to as low as 50 ng of total RNA. The A260/A280
ratio should be between 1.8 and 2.1 for pure RNA. Upon receipt of the RNA
samples Gene Express assesses their concentrations and A260/A280
ratios using a NanoDrop® ND-1000 spectrophotometer. The integrity
of the RNA is analyzed using the RNA 6000 Nano Assay on an Agilent 2100
Bioanalyzer. If the resulting electropherogram (example)
meets the quality parameters, Gene Express proceeds with the processing
of the sample.
The Gene Expression Analysis Service follows this general
workflow for the standard protocol (technology and graphical
overview):
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