ParAllele Press Release

Affymetrix, ParAllele and Cambridge University Collaborate For Large-Scale Genetic Study of Diabetes

-- Candidate-gene association study to use standard panel of more than 10,000 coding SNP's and genotype over 2,000 people --

Professor John Todd of the University's Juvenile Diabetes Research Foundation/ Wellcome Trust Diabetes and Inflammation Laboratory (DIL) at Cambridge is leading this research effort. His group will be the first to use a ParAllele-developed standard panel of 10,000 non-synonymous SNPs SNPs that change the sequences of proteins to compare genotypes between 1,000 control samples and 1,000 diabetic samples. The scientists have planned this as the first stage in the analysis of over 20,000 DNA samples already collected from diabetes patients and their relatives. The DIL is committed to sharing these samples and results with other researchers in the world-wide effort of finding new disease-associated genes for the development of better therapies and prognostic tests. The controls come from the 1958 British Birth Cohort in collaboration with Professor David Strachan of St. George's Hospital Medical School, London.

"This research project is the most exciting and important genetics experiment I've ever been involved in", said Todd. "We've been collecting samples for quite some time and have been waiting for a technology that would give us the genetic power we needed to commence informative studies. Using this new solution from Affymetrix and ParAllele for a genome-wide gene association study provides us with the best opportunity we've ever had to discover new disease-associated genes and polymorphisms."

"We're delighted to offer scientists a full range of tools to analyze the genome in different ways, leading to a better understanding of disease", said Greg Yap, Senior Marketing Director of DNA Analysis at Affymetrix. "Our new partnership with ParAllele enables us to provide researchers with another solution for genetic association studies and complements our existing solutions for genome-wide genotyping and resequencing."

ParAllele's MegAllele products include genotyping reagent kits and software specifically designed for use with Affymetrix GeneChip® Tag Arrays and instrumentation systems. These new products offer the ability to genotype up to tens of thousands of SNPs in a single, flexible assay.

"We are pleased to be working with a pioneer such as John Todd on such an important study", said Nick Naclerio, President & CEO of ParAllele BioScience. "This will be the first time that any researcher has directly analyzed this many potentially disease-related SNPs in such a well-characterized population. The ability to conduct studies of this scale may provide important new insights into type I diabetes."

Using the combined MegAllele and GeneChip product, scientists can select SNPs from custom panels of 3,000 to 5,000 SNPs and standard panels of up to 10,000 pre-selected SNPs. The panel being used in the Cambridge University study is also available to other researchers worldwide. Assay design is customized and comprehensive, enabling researchers to successfully genotype more of the SNPs they want.

About the Juvenile Diabetes Research Foundation/Wellcome Trust Diabetes and Inflammation Laboratory (DIL)

About Affymetrix

About ParAllele BioScience

Headquartered in South San Francisco, California, ParAllele BioScience was founded by a team of leading researchers from the Stanford Genome Technology Center and Uppsala University. The company's investors include Abingworth Management, Index Ventures, Mohr Davidow Ventures, and Versant Ventures. For more information about ParAllele, please visit the company's website at: parallelebio.com.

All statements in this press release that are not historical are "forward-looking statements" within the meaning of Section 21E of the Securities Exchange Act as amended, including statements regarding Affymetrix' "expectations," "beliefs," "hopes," "intentions," "strategies" or the like. Such statements are subject to risks and uncertainties that could cause actual results to differ materially for Affymetrix from those projected, including, but not limited to risks of the Company's ability to achieve and sustain higher levels of revenue, higher gross margins, reduced operating expenses, uncertainties relating to technological approaches, manufacturing, product development, market acceptance (including uncertainties relating to product development and market acceptance of the Affymetrix and ParAllele collaboration), personnel retention, uncertainties related to cost and pricing of Affymetrix products, dependence on collaborative partners, uncertainties relating to sole source suppliers, uncertainties relating to FDA and other regulatory approvals, competition, risks relating to intellectual property of others and the uncertainties of patent protection and litigation. These and other risk factors are discussed in Affymetrix' Form 10-K for the year ended December 31, 2003 and other SEC reports, including its Quarterly Reports on Form 10-Q for subsequent quarterly periods. Affymetrix expressly disclaims any obligation or undertaking to release publicly any updates or revisions to any forward-looking statements contained herein to reflect any change in Affymetrix' expectations with regard thereto or any change in events, conditions, or circumstances on which any such statements are based.

NOTE: Affymetrix, the Affymetrix logo, and GeneChip are registered trademarks owned or used by Affymetrix, Inc.