Affymetrix (AFFX) was down 23.6% in preopen Island trading after the genetic technology company warned late Monday that it expects to report a second-quarter loss of $4 to $7 million.

This morning, Robertson Stephens cut its rating on the stock to market perform from buy, while Credit Suisse First Boston cut estimates for Affymetrix's 2001 results to a loss of 30 cents a share from a profit of 14 cents. CSFB also cut estimates for 2002 and 2003.

The stock fell about 8% Tuesday prior to the company's announcement after pharmaceutical company GlaxoSmithKline ( GSK) cut its stake in the company to 13.4% from 14.5%.