Affymetrix ( AFFX)was off more than 15% Thursday after the biotech chip maker reported Wednesday a wider-than-expected first quarter loss and slowing sales for the rest of the year.

In recent trading, shares in the company, which sells chips embedded with DNA material for use in genetic research, were off $5.45, or 15.3%, to $30.05 in Thursday trading.

On Wednesday, Affymetrix posted a net loss of $6 million, or 11 cents per share in the first quarter, missing Wall Street estimates by 7 cents. The company said sales were off because of a recall of one of its chip products due to a design error. The recall and replacement of the chip, or Murine U74 genome array, will hurt sales into the third quarter of the year, dropping 2001 revenue to the low end of projections, now forecast to be $260 million to $290 million.

Sales of other chip products, as well as the equipment used to analyze them, were not affected and met growth targets, the company said.

On Thursday, Robertson Stephens analyst Mike King downgraded Affymetrix to buy from strong buy. His firm has done banking for Affymetrix.

UBS Warburg analyst Jeannie Lorenz cut her 12-month price target to $45 per share from $95 per share, while maintaining her buy rating. Her firm doesn't do banking for Affymetrix.