Gene array expression measurements

Wodicka et al. (1997) created such an array for measuring yeasf gene expression based upon 25-mer oligonucleotides covering 6200 ORFs. Each ORF was represented by 20 PM and 20 MM probes. Why so many probes Simply put, not all probes hybridize in a predictable manner. Averaging across a number of probes improves the outcome. Thus, the yeast expression chip comprised over 65,000 probe features and required a set of four chip subarrays. 

For the pituitary hormones, and pancreatic hormones, analytical methods are in general available with species specific reagents for the mouse, rat, dog, pig and to a limited extent for rabbit. Steroid hormones can be measured readily by an array of analytical methods. Application of gene arrays and studies on gene expression are not recommended for single-dose experiments, repeated dose exposure is required (3-7 days). 

Ronald, J., Akey, J.M., Whittle, J., Smith, E.N., Yvert, G., and Kruglyak, L. 2005. Simultaneous genotyping, gene expression measurement, and detection of allele-specific expression with oligonucleotide arrays. Gen. Res. 15,284-291. 

N. P. Gerry, M.E. Lenburg, C.L. Rosenberg, Reliability and reproducibility of gene expression measurements using amplified RNA from laser-microdissected primary breast tissue with oligonucleotide arrays, J. Mol. Diagn. 2005, 7, 57-64. 

Spurgeon, S. L., R. C. Jones, and R. Ramakrishnan. 2008. High throughput gene expression measurement with real time PCR in a microfluidic dynamic array. PLoS One... 

There are many protocols and different types of platforms available, e.g. GeneChips from Affymetrix, Illumina Bead Arrays, Arrays from Agilent, Applied Biosystems, GE Healthcare, customized spotted cDNA microarrays etc. the basic procedure for a large-scale measurement of gene expression involves the preparation of total or mRNA from the biological sample(s) under investigation (e.g. candidate tissue) and the hybridization of copied labelled RNA or cDNA to the DNA elements on the array surface (Fig. 1). 

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